2004-11-03 13:51:07 +00:00
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.\" This manpage is copyright (C) 1992 Drew Eckhardt,
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.\" copyright (C) 1995 Michael Shields.
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.\"
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intro.1, _exit.2, access.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bind.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, close.2, connect.2, delete_module.2, dup.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, fork.2, fstatat.2, fsync.2, futimesat.2, get_robust_list.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getpagesize.2, getpid.2, getresuid.2, getrlimit.2, getrusage.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, idle.2, init_module.2, intro.2, iopl.2, kcmp.2, kexec_load.2, kill.2, link.2, linkat.2, llseek.2, lookup_dcookie.2, madvise.2, mincore.2, mkdirat.2, mknodat.2, mmap.2, mmap2.2, mount.2, mprotect.2, mq_getsetattr.2, msgctl.2, msgget.2, msgop.2, msync.2, nice.2, open.2, openat.2, pause.2, perfmonctl.2, personality.2, pipe.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, quotactl.2, read.2, readahead.2, readdir.2, readlinkat.2, readv.2, reboot.2, recvmmsg.2, remap_file_pages.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, select.2, select_tut.2, semctl.2, semget.2, semop.2, sendmmsg.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setresuid.2, setuid.2, setup.2, sgetmask.2, shmctl.2, shmget.2, shmop.2, sigaction.2, sigaltstack.2, signal.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, splice.2, stat.2, statfs.2, stime.2, subpage_prot.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, syscalls.2, sysctl.2, sysfs.2, syslog.2, tee.2, time.2, timer_create.2, timer_delete.2, timer_getoverrun.2, timer_settime.2, times.2, tkill.2, umask.2, umount.2, uname.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, abort.3, abs.3, acos.3, acosh.3, adjtime.3, aio_init.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, byteorder.3, bzero.3, catgets.3, catopen.3, cbrt.3, ceil.3, clearenv.3, clock.3, clock_getcpuclockid.3, closedir.3, confstr.3, copysign.3, cos.3, cosh.3, ctermid.3, ctime.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, end.3, endian.3, erf.3, erfc.3, ether_aton.3, euidaccess.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, fcloseall.3, fexecve.3, ffs.3, fgetgrent.3, fgetpwent.3, finite.3, flockfile.3, floor.3, fmod.3, fnmatch.3, fopencookie.3, fpathconf.3, fpurge.3, frexp.3, fseeko.3, ftok.3, futimes.3, gcvt.3, get_nprocs_conf.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getcontext.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getenv.3, getfsent.3, getgrent.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getifaddrs.3, getipnodebyname.3, getline.3, getlogin.3, getmntent.3, getnetent.3, getnetent_r.3, getopt.3, getprotoent.3, getprotoent_r.3, getpw.3, getpwent.3, getpwnam.3, getrpcent_r.3, gets.3, getservent.3, getservent_r.3, getumask.3, getusershell.3, getutmp.3, getw.3, glob.3, gnu_get_libc_version.3, gsignal.3, hypot.3, if_nameindex.3, if_nametoindex.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, j0.3, ldexp.3, localeconv.3, log.3, log10.3, log1p.3, log2.3, logb.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, mallinfo.3, malloc.3, malloc_get_state.3, malloc_info.3, malloc_stats.3, malloc_trim.3, malloc_usable_size.3, mallopt.3, matherr.3, mcheck.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, on_exit.3, opendir.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, profil.3, psignal.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_attr_setdetachstate.3, pthread_attr_setguardsize.3, pthread_attr_setinheritsched.3, pthread_attr_setschedparam.3, pthread_attr_setschedpolicy.3, pthread_attr_setscope.3, pthread_attr_setstack.3, pthread_attr_setstackaddr.3, pthread_attr_setstacksize.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_cleanup_push_defer_np.3, pthread_create.3, pthread_detach.3, pthread_equal.3, pthread_exit.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_join.3, pthread_kill.3, pthread_kill_other_threads_np.3, pthread_self.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setname_np.3, pthread_setschedparam.3, pthread_setschedprio.3, pthread_sigmask.3, pthread_sigqueue.3, pthread_testcancel.3, pthread_tryjoin_np.3, pthread_yield.3, putenv.3, putpwent.3, puts.3, qecvt.3, qsort.3, raise.3, rand.3, random.3, random_r.3, re_comp.3, readdir.3, realpath.3, regex.3, remainder.3, remove.3, resolver.3, rewinddir.3, rint.3, round.3, scalb.3, scalbln.3, scandir.3, sched_getcpu.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setenv.3, setlocale.3, setlogmask.3, shm_open.3, siginterrupt.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sigwait.3, sin.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdio_ext.3, stpcpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfry.3, strftime.3, string.3, strlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, trunc.3, tsearch.3, ttyslot.3, tzset.3, ulimit.3, undocumented.3, unlocked_stdio.3, usleep.3, y0.3, cpuid.4, full.4, initrd.4, mouse.4, msr.4, sd.4, st.4, acct.5, core.5, services.5, slabinfo.5, aio.7, capabilities.7, credentials.7, feature_test_macros.7, hier.7, inotify.7, libc.7, locale.7, man-pages.7, man.7, math_error.7, mq_overview.7, numa.7, path_resolution.7, pipe.7, pthreads.7, pty.7, rtld-audit.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, suffixes.7, svipc.7, termio.7, time.7, udplite.7, units.7, uri.7, sln.8: s/LICENSE_START(verbatim)/LICENSE_START(VERBATIM)/
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-10 09:29:01 +00:00
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.\" %%%LICENSE_START(VERBATIM)
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2004-11-03 13:51:07 +00:00
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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intro.1, _exit.2, access.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bind.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, close.2, connect.2, delete_module.2, dup.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, fork.2, fstatat.2, fsync.2, futimesat.2, get_robust_list.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getpagesize.2, getpid.2, getresuid.2, getrlimit.2, getrusage.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, idle.2, init_module.2, intro.2, iopl.2, kcmp.2, kexec_load.2, kill.2, link.2, linkat.2, llseek.2, lookup_dcookie.2, madvise.2, mincore.2, mkdirat.2, mknodat.2, mmap.2, mmap2.2, mount.2, mprotect.2, mq_getsetattr.2, msgctl.2, msgget.2, msgop.2, msync.2, nice.2, open.2, openat.2, pause.2, perfmonctl.2, personality.2, pipe.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, quotactl.2, read.2, readahead.2, readdir.2, readlinkat.2, readv.2, reboot.2, recvmmsg.2, remap_file_pages.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, select.2, select_tut.2, semctl.2, semget.2, semop.2, sendmmsg.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setresuid.2, setuid.2, setup.2, sgetmask.2, shmctl.2, shmget.2, shmop.2, sigaction.2, sigaltstack.2, signal.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, splice.2, stat.2, statfs.2, stime.2, subpage_prot.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, syscalls.2, sysctl.2, sysfs.2, syslog.2, tee.2, time.2, timer_create.2, timer_delete.2, timer_getoverrun.2, timer_settime.2, times.2, tkill.2, umask.2, umount.2, uname.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, abort.3, abs.3, acos.3, acosh.3, adjtime.3, aio_init.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, byteorder.3, bzero.3, catgets.3, catopen.3, cbrt.3, ceil.3, clearenv.3, clock.3, clock_getcpuclockid.3, closedir.3, confstr.3, copysign.3, cos.3, cosh.3, ctermid.3, ctime.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, end.3, endian.3, erf.3, erfc.3, ether_aton.3, euidaccess.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, fcloseall.3, fexecve.3, ffs.3, fgetgrent.3, fgetpwent.3, finite.3, flockfile.3, floor.3, fmod.3, fnmatch.3, fopencookie.3, fpathconf.3, fpurge.3, frexp.3, fseeko.3, ftok.3, futimes.3, gcvt.3, get_nprocs_conf.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getcontext.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getenv.3, getfsent.3, getgrent.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getifaddrs.3, getipnodebyname.3, getline.3, getlogin.3, getmntent.3, getnetent.3, getnetent_r.3, getopt.3, getprotoent.3, getprotoent_r.3, getpw.3, getpwent.3, getpwnam.3, getrpcent_r.3, gets.3, getservent.3, getservent_r.3, getumask.3, getusershell.3, getutmp.3, getw.3, glob.3, gnu_get_libc_version.3, gsignal.3, hypot.3, if_nameindex.3, if_nametoindex.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, j0.3, ldexp.3, localeconv.3, log.3, log10.3, log1p.3, log2.3, logb.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, mallinfo.3, malloc.3, malloc_get_state.3, malloc_info.3, malloc_stats.3, malloc_trim.3, malloc_usable_size.3, mallopt.3, matherr.3, mcheck.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, on_exit.3, opendir.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, profil.3, psignal.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_attr_setdetachstate.3, pthread_attr_setguardsize.3, pthread_attr_setinheritsched.3, pthread_attr_setschedparam.3, pthread_attr_setschedpolicy.3, pthread_attr_setscope.3, pthread_attr_setstack.3, pthread_attr_setstackaddr.3, pthread_attr_setstacksize.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_cleanup_push_defer_np.3, pthread_create.3, pthread_detach.3, pthread_equal.3, pthread_exit.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_join.3, pthread_kill.3, pthread_kill_other_threads_np.3, pthread_self.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setname_np.3, pthread_setschedparam.3, pthread_setschedprio.3, pthread_sigmask.3, pthread_sigqueue.3, pthread_testcancel.3, pthread_tryjoin_np.3, pthread_yield.3, putenv.3, putpwent.3, puts.3, qecvt.3, qsort.3, raise.3, rand.3, random.3, random_r.3, re_comp.3, readdir.3, realpath.3, regex.3, remainder.3, remove.3, resolver.3, rewinddir.3, rint.3, round.3, scalb.3, scalbln.3, scandir.3, sched_getcpu.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setenv.3, setlocale.3, setlogmask.3, shm_open.3, siginterrupt.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sigwait.3, sin.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdio_ext.3, stpcpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfry.3, strftime.3, string.3, strlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, trunc.3, tsearch.3, ttyslot.3, tzset.3, ulimit.3, undocumented.3, unlocked_stdio.3, usleep.3, y0.3, cpuid.4, full.4, initrd.4, mouse.4, msr.4, sd.4, st.4, acct.5, core.5, services.5, slabinfo.5, aio.7, capabilities.7, credentials.7, feature_test_macros.7, hier.7, inotify.7, libc.7, locale.7, man-pages.7, man.7, math_error.7, mq_overview.7, numa.7, path_resolution.7, pipe.7, pthreads.7, pty.7, rtld-audit.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, suffixes.7, svipc.7, termio.7, time.7, udplite.7, units.7, uri.7, sln.8: Global fix: Add LICENSE_START(verbatim)
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-10 09:28:40 +00:00
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.\" %%%LICENSE_END
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2004-11-03 13:51:07 +00:00
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.\"
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.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
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.\" Modified 1995-05-18 by Jim Van Zandt <jrv@vanzandt.mv.com>
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.\" Sun Feb 11 14:07:00 MET 1996 Martin Schulze <joey@linux.de>
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.\" * layout slightly modified
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.\"
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.\" Modified Mon Oct 21 23:05:29 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified Thu Feb 24 01:41:09 CET 2000 by aeb
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.\" Modified Thu Feb 9 22:32:09 CET 2001 by bert hubert <ahu@ds9a.nl>, aeb
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.\" Modified Mon Nov 11 14:35:00 PST 2002 by Ben Woodard <ben@zork.net>
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2006-03-12 03:09:50 +00:00
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.\" 2005-03-11, mtk, modified pselect() text (it is now a system
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.\" call in 2.6.16.
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2004-11-03 13:51:07 +00:00
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.\"
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intro.1, locale.1, _exit.2, access.2, bpf.2, brk.2, capget.2, chmod.2, chroot.2, clock_getres.2, clone.2, eventfd.2, fallocate.2, fork.2, getgroups.2, gethostname.2, getpid.2, getpriority.2, getrlimit.2, getrusage.2, gettid.2, iopl.2, ioprio_set.2, killpg.2, mlock.2, mprotect.2, perf_event_open.2, poll.2, posix_fadvise.2, pread.2, ptrace.2, read.2, readv.2, recv.2, rename.2, sched_setaffinity.2, sched_setattr.2, seccomp.2, select.2, send.2, seteuid.2, setgid.2, setresuid.2, setreuid.2, setuid.2, sigaltstack.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, socket.2, stat.2, timer_create.2, uname.2, utimensat.2, wait.2, wait4.2, write.2, MB_LEN_MAX.3, __ppc_get_timebase.3, clearenv.3, dl_iterate_phdr.3, error.3, fexecve.3, fpurge.3, fread.3, fts.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getgrent_r.3, gethostbyname.3, getifaddrs.3, getnameinfo.3, getnetent_r.3, getprotoent.3, getprotoent_r.3, getpw.3, getpwent_r.3, getrpcent.3, getrpcent_r.3, getrpcport.3, getservent.3, getservent_r.3, gsignal.3, key_setsecret.3, malloc_get_state.3, malloc_info.3, malloc_stats.3, malloc_trim.3, memcpy.3, mq_notify.3, mq_open.3, perror.3, profil.3, psignal.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_create.3, pthread_detach.3, pthread_getattr_np.3, pthread_join.3, pthread_setname_np.3, pthread_tryjoin_np.3, putgrent.3, rcmd.3, rpc.3, rpmatch.3, sem_close.3, sem_open.3, setaliasent.3, shm_open.3, sigqueue.3, strfmon.3, xcrypt.3, xdr.3, console_codes.4, null.4, core.5, host.conf.5, hosts.equiv.5, locale.5, repertoiremap.5, locale.7, man-pages.7, pty.7, rtld-audit.7, sched.7, vdso.7: tstamp
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2015-07-23 14:12:28 +00:00
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.TH SELECT 2 2015-07-23 "Linux" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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2007-04-12 22:42:49 +00:00
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select, pselect, FD_CLR, FD_ISSET, FD_SET, FD_ZERO \-
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2006-12-27 03:54:41 +00:00
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synchronous I/O multiplexing
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2004-11-03 13:51:07 +00:00
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.SH SYNOPSIS
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2006-03-07 02:25:37 +00:00
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.nf
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2015-04-18 06:10:32 +00:00
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/* According to POSIX.1-2001, POSIX.1-2008 */
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2004-11-03 13:51:07 +00:00
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.br
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.B #include <sys/select.h>
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.sp
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/* According to earlier standards */
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.br
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.B #include <sys/time.h>
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.br
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.B #include <sys/types.h>
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.br
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.B #include <unistd.h>
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.sp
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2007-07-08 12:11:40 +00:00
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.BI "int select(int " nfds ", fd_set *" readfds ", fd_set *" writefds ,
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.BI " fd_set *" exceptfds ", struct timeval *" timeout );
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2004-11-03 13:51:07 +00:00
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.sp
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2006-02-02 18:15:36 +00:00
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.BI "void FD_CLR(int " fd ", fd_set *" set );
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2004-11-03 13:51:07 +00:00
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.br
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2007-04-03 14:04:54 +00:00
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.BI "int FD_ISSET(int " fd ", fd_set *" set );
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2004-11-03 13:51:07 +00:00
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.br
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2006-02-02 18:15:36 +00:00
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.BI "void FD_SET(int " fd ", fd_set *" set );
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2004-11-03 13:51:07 +00:00
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.br
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2006-02-02 18:15:36 +00:00
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.BI "void FD_ZERO(fd_set *" set );
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2006-03-19 23:32:26 +00:00
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.sp
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.B #include <sys/select.h>
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.sp
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2007-07-08 12:11:40 +00:00
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.BI "int pselect(int " nfds ", fd_set *" readfds ", fd_set *" writefds ,
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.BI " fd_set *" exceptfds ", const struct timespec *" timeout ,
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.BI " const sigset_t *" sigmask );
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2004-11-03 13:51:07 +00:00
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.fi
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2007-07-08 12:11:40 +00:00
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR pselect ():
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_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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and
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2006-04-21 18:17:12 +00:00
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allow a program to monitor multiple file descriptors,
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2006-04-21 10:41:09 +00:00
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waiting until one or more of the file descriptors become "ready"
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for some class of I/O operation (e.g., input possible).
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2006-04-21 18:17:12 +00:00
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A file descriptor is considered ready if it is possible to
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poll.2, select.2: fix erroneous description of "available for write".
POSIX says: "POLLOUT Normal data may be written without
blocking.". This is "may" is misleading, see the POSIX
write page:
Write requests to a pipe or FIFO shall be handled in the
same way as a regular file with the following exceptions:
...
If the O_NONBLOCK flag is clear, a write request may cause
the thread to block, but on normal completion it shall
return nbyte.
...
When attempting to write to a file descriptor (other than a
pipe or FIFO) that supports non-blocking writes and cannot
accept the data immediately:
If the O_NONBLOCK flag is clear, write() shall block the
calling thread until the data can be accepted.
If the O_NONBLOCK flag is set, write() shall not block the
thread. If some data can be written without blocking the
thread, write() shall write what it can and return the
number of bytes written. Otherwise, it shall return -1 and
set errno to [EAGAIN].
The net result is that write() of more than 1 byte on a
socket, pipe or FIFO which is "ready" may block: write()
(unlike read!) will attempt to write the entire buffer and
only return a short write under exceptional circumstances.
Indeed, this is the behaviour we see in Linux:
https://github.com/rustyrussell/ccan/commit/897626152d12d7fd13a8feb36989eb5c8c1f3485
https://plus.google.com/103188246877163594460/posts/BkTGTMHDFgZ
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2014-08-19 13:57:21 +00:00
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perform a corresponding I/O operation (e.g.,
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.BR read (2)
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without blocking, or a sufficiently small
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.BR write (2)).
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2004-11-03 13:51:07 +00:00
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.PP
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2006-04-21 10:41:09 +00:00
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The operation of
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.BR select ()
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and
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.BR pselect ()
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2012-08-17 05:51:43 +00:00
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is identical, other than these three differences:
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2004-11-03 13:51:07 +00:00
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.TP
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(i)
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2006-03-07 02:25:37 +00:00
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uses a timeout that is a
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2004-11-03 13:51:07 +00:00
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.I struct timeval
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(with seconds and microseconds), while
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2004-11-03 13:51:07 +00:00
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uses a
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.I struct timespec
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(with seconds and nanoseconds).
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.TP
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(ii)
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2006-03-07 02:25:37 +00:00
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may update the
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2004-11-03 13:51:07 +00:00
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.I timeout
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2006-03-07 02:25:37 +00:00
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argument to indicate how much time was left.
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2006-03-07 02:25:37 +00:00
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does not change this argument.
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2004-11-03 13:51:07 +00:00
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.TP
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(iii)
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2006-03-07 02:25:37 +00:00
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has no
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2004-11-03 13:51:07 +00:00
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.I sigmask
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2006-03-07 02:25:37 +00:00
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argument, and behaves as
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2004-11-03 13:51:07 +00:00
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called with NULL
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.IR sigmask .
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.PP
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2007-04-12 22:42:49 +00:00
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Three independent sets of file descriptors are watched.
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2006-04-20 21:21:42 +00:00
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Those listed in
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2004-11-03 13:51:07 +00:00
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.I readfds
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will be watched to see if characters become
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available for reading (more precisely, to see if a read will not
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2005-07-06 06:54:27 +00:00
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block; in particular, a file descriptor is also ready on end-of-file),
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2004-11-03 13:51:07 +00:00
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those in
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.I writefds
|
poll.2, select.2: fix erroneous description of "available for write".
POSIX says: "POLLOUT Normal data may be written without
blocking.". This is "may" is misleading, see the POSIX
write page:
Write requests to a pipe or FIFO shall be handled in the
same way as a regular file with the following exceptions:
...
If the O_NONBLOCK flag is clear, a write request may cause
the thread to block, but on normal completion it shall
return nbyte.
...
When attempting to write to a file descriptor (other than a
pipe or FIFO) that supports non-blocking writes and cannot
accept the data immediately:
If the O_NONBLOCK flag is clear, write() shall block the
calling thread until the data can be accepted.
If the O_NONBLOCK flag is set, write() shall not block the
thread. If some data can be written without blocking the
thread, write() shall write what it can and return the
number of bytes written. Otherwise, it shall return -1 and
set errno to [EAGAIN].
The net result is that write() of more than 1 byte on a
socket, pipe or FIFO which is "ready" may block: write()
(unlike read!) will attempt to write the entire buffer and
only return a short write under exceptional circumstances.
Indeed, this is the behaviour we see in Linux:
https://github.com/rustyrussell/ccan/commit/897626152d12d7fd13a8feb36989eb5c8c1f3485
https://plus.google.com/103188246877163594460/posts/BkTGTMHDFgZ
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2014-08-19 13:57:21 +00:00
|
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will be watched to see if space is available for write (though a large
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write may still block), and those in
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2004-11-03 13:51:07 +00:00
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.I exceptfds
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2007-04-12 22:42:49 +00:00
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will be watched for exceptions.
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On exit, the sets are modified in place
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2006-04-20 21:21:42 +00:00
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to indicate which file descriptors actually changed status.
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Each of the three file descriptor sets may be specified as NULL
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2007-04-12 22:42:49 +00:00
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if no file descriptors are to be watched for the corresponding class
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2006-04-20 21:21:42 +00:00
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of events.
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2004-11-03 13:51:07 +00:00
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.PP
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Four macros are provided to manipulate the sets.
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2005-10-19 06:54:38 +00:00
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.BR FD_ZERO ()
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2006-02-02 18:18:55 +00:00
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clears a set.
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2005-10-19 06:54:38 +00:00
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.BR FD_SET ()
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2004-11-03 13:51:07 +00:00
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and
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2005-10-19 06:54:38 +00:00
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.BR FD_CLR ()
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2006-04-20 21:21:42 +00:00
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respectively add and remove a given file descriptor from a set.
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2005-10-19 06:54:38 +00:00
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.BR FD_ISSET ()
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2007-04-12 22:42:49 +00:00
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tests to see if a file descriptor is part of the set;
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2006-04-20 21:21:42 +00:00
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this is useful after
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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returns.
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.PP
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2006-05-13 06:08:41 +00:00
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.I nfds
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2006-04-20 21:21:42 +00:00
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is the highest-numbered file descriptor in any of the three sets, plus 1.
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2004-11-03 13:51:07 +00:00
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.PP
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2012-05-01 19:54:53 +00:00
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The
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2004-11-03 13:51:07 +00:00
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.I timeout
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2013-09-04 08:15:18 +00:00
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argument specifies the interval that
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2012-05-01 19:54:53 +00:00
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should block waiting for a file descriptor to become ready.
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2014-01-31 06:47:22 +00:00
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The call will block until either:
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.IP * 3
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a file descriptor becomes ready;
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.IP *
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the call is interrupted by a signal handler; or
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.IP *
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2014-03-16 10:15:27 +00:00
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the timeout expires.
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2014-01-31 06:47:22 +00:00
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.PP
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Note that the
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.I timeout
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interval will be rounded up to the system clock granularity,
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2012-05-01 19:54:53 +00:00
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and kernel scheduling delays mean that the blocking interval
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2013-09-04 08:15:18 +00:00
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may overrun by a small amount.
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2008-07-14 21:17:23 +00:00
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If both fields of the
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.I timeval
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2010-06-20 01:44:37 +00:00
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structure are zero, then
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2008-07-14 21:17:23 +00:00
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returns immediately.
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2007-04-12 22:42:49 +00:00
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(This is useful for polling.)
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If
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2004-11-03 13:51:07 +00:00
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.I timeout
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is NULL (no timeout),
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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can block indefinitely.
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.PP
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.I sigmask
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is a pointer to a signal mask (see
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.BR sigprocmask (2));
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if it is not NULL, then
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2004-11-03 13:51:07 +00:00
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first replaces the current signal mask by the one pointed to by
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.IR sigmask ,
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2007-12-18 07:47:22 +00:00
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then does the "select" function, and then restores the original
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2006-03-07 02:25:37 +00:00
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signal mask.
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2004-11-03 13:51:07 +00:00
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.PP
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2006-03-12 03:09:50 +00:00
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Other than the difference in the precision of the
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.I timeout
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2007-04-12 22:42:49 +00:00
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argument, the following
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2006-03-12 03:09:50 +00:00
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.BR pselect ()
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call:
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.nf
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2007-04-12 22:42:49 +00:00
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ready = pselect(nfds, &readfds, &writefds, &exceptfds,
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2006-03-12 03:09:50 +00:00
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timeout, &sigmask);
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.fi
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is equivalent to
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.I atomically
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executing the following calls:
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.nf
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sigset_t origmask;
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2012-08-19 20:03:42 +00:00
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pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
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2006-03-12 03:09:50 +00:00
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ready = select(nfds, &readfds, &writefds, &exceptfds, timeout);
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2012-08-19 20:03:42 +00:00
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pthread_sigmask(SIG_SETMASK, &origmask, NULL);
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2006-03-12 03:09:50 +00:00
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.fi
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.PP
|
2007-04-12 22:42:49 +00:00
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The reason that
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2006-03-12 03:09:50 +00:00
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is needed is that if one wants to wait for either a signal
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or for a file descriptor to become ready, then
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2007-04-12 22:42:49 +00:00
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an atomic test is needed to prevent race conditions.
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2006-03-12 03:09:50 +00:00
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(Suppose the signal handler sets a global flag and
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2007-04-12 22:42:49 +00:00
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returns.
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Then a test of this global flag followed by a call of
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2004-11-03 13:51:07 +00:00
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.BR select ()
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could hang indefinitely if the signal arrived just after the test
|
2007-04-12 22:42:49 +00:00
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but just before the call.
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2006-03-12 03:09:50 +00:00
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By contrast,
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2005-10-19 06:54:38 +00:00
|
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.BR pselect ()
|
2004-11-03 13:51:07 +00:00
|
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allows one to first block signals, handle the signals that have come in,
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then call
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.BR pselect ()
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with the desired
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.IR sigmask ,
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avoiding the race.)
|
intro.1, time.1, _syscall.2, accept.2, capget.2, clone.2, execve.2, fcntl.2, intro.2, ioctl_list.2, ioprio_set.2, kill.2, mlock.2, nanosleep.2, perf_event_open.2, select.2, stat.2, times.2, ustat.2, vfork.2, wait.2, cfree.3, dbopen.3, dlopen.3, fenv.3, fmtmsg.3, gamma.3, getaddrinfo.3, gethostbyname.3, getnameinfo.3, getspnam.3, login.3, printf.3, regex.3, stdio.3, sysconf.3, termios.3, ttyslot.3, undocumented.3, wordexp.3, console_codes.4, initrd.4, mouse.4, random.4, st.4, tty_ioctl.4, wavelan.4, charmap.5, dir_colors.5, hosts.5, termcap.5, armscii-8.7, boot.7, bootparam.7, capabilities.7, charsets.7, ddp.7, futex.7, glob.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man.7, numa.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, rtnetlink.7, signal.7, time.7, udp.7, udplite.7, unicode.7, uri.7, utf-8.7: G;lobal fix: remove unneeded double quotes in .SS headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:02:18 +00:00
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.SS The timeout
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2004-11-03 13:51:07 +00:00
|
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The time structures involved are defined in
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.I <sys/time.h>
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and look like
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2007-12-19 06:57:44 +00:00
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.in +4n
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2004-11-03 13:51:07 +00:00
|
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.nf
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2007-04-12 22:42:49 +00:00
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struct timeval {
|
2004-11-03 13:51:07 +00:00
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long tv_sec; /* seconds */
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long tv_usec; /* microseconds */
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};
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.fi
|
2007-12-19 05:53:30 +00:00
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.in
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2004-11-03 13:51:07 +00:00
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and
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2007-12-19 06:57:44 +00:00
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.in +4n
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2004-11-03 13:51:07 +00:00
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.nf
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struct timespec {
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long tv_sec; /* seconds */
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long tv_nsec; /* nanoseconds */
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};
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.fi
|
2007-12-19 05:53:30 +00:00
|
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.in
|
2004-11-03 13:51:07 +00:00
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|
|
|
2015-04-18 06:10:32 +00:00
|
|
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(However, see below on the POSIX.1 versions.)
|
2004-11-03 13:51:07 +00:00
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|
|
.PP
|
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Some code calls
|
2005-10-19 06:54:38 +00:00
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.BR select ()
|
2004-11-03 13:51:07 +00:00
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with all three sets empty,
|
2006-12-27 02:48:57 +00:00
|
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.I nfds
|
2006-04-20 21:21:42 +00:00
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zero, and a non-NULL
|
2004-11-03 13:51:07 +00:00
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.I timeout
|
|
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|
as a fairly portable way to sleep with subsecond precision.
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.PP
|
2007-04-12 22:42:49 +00:00
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On Linux,
|
2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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modifies
|
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.I timeout
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to reflect the amount of time not slept; most other implementations
|
2006-03-07 22:38:11 +00:00
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|
do not do this.
|
2015-04-18 06:10:32 +00:00
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(POSIX.1 permits either behavior.)
|
2006-03-07 22:38:11 +00:00
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This causes problems both when Linux code which reads
|
2004-11-03 13:51:07 +00:00
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|
.I timeout
|
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|
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is ported to other operating systems, and when code is ported to Linux
|
2007-06-13 22:13:46 +00:00
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that reuses a \fIstruct timeval\fP for multiple
|
2005-10-19 06:54:38 +00:00
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|
.BR select ()s
|
2007-04-12 22:42:49 +00:00
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in a loop without reinitializing it.
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Consider
|
2004-11-03 13:51:07 +00:00
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.I timeout
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|
to be undefined after
|
2005-10-19 06:54:38 +00:00
|
|
|
.BR select ()
|
2004-11-03 13:51:07 +00:00
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returns.
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2007-06-08 09:56:56 +00:00
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.\" .PP - it is rumored that:
|
2004-11-03 13:51:07 +00:00
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|
.\" On BSD, when a timeout occurs, the file descriptor bits are not changed.
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.\" - it is certainly true that:
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.\" Linux follows SUSv2 and sets the bit masks to zero upon a timeout.
|
getent.1, intro.1, time.1, _exit.2, _syscall.2, accept.2, access.2, acct.2, adjtimex.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bdflush.2, bind.2, brk.2, cacheflush.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, clone.2, close.2, connect.2, create_module.2, delete_module.2, dup.2, epoll_create.2, epoll_ctl.2, epoll_wait.2, eventfd.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, flock.2, fork.2, fstatat.2, fsync.2, futex.2, futimesat.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getitimer.2, getpagesize.2, getpeername.2, getpid.2, getpriority.2, getresuid.2, getrlimit.2, getrusage.2, getsid.2, getsockname.2, getsockopt.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, getxattr.2, idle.2, init_module.2, inotify_add_watch.2, inotify_init.2, inotify_rm_watch.2, intro.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, ioprio_set.2, ipc.2, kcmp.2, kill.2, killpg.2, link.2, linkat.2, listen.2, listxattr.2, llseek.2, lookup_dcookie.2, lseek.2, madvise.2, migrate_pages.2, mincore.2, mkdir.2, mkdirat.2, mknod.2, mknodat.2, mlock.2, mmap.2, mmap2.2, modify_ldt.2, mount.2, move_pages.2, mprotect.2, mq_getsetattr.2, mremap.2, msgctl.2, msgget.2, msgop.2, msync.2, nanosleep.2, nfsservctl.2, nice.2, open.2, openat.2, outb.2, pause.2, pciconfig_read.2, perf_event_open.2, perfmonctl.2, personality.2, pipe.2, pivot_root.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, ptrace.2, query_module.2, quotactl.2, read.2, readahead.2, readdir.2, readlink.2, readlinkat.2, readv.2, reboot.2, recv.2, remap_file_pages.2, removexattr.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, sched_get_priority_max.2, sched_rr_get_interval.2, sched_setaffinity.2, sched_setparam.2, sched_setscheduler.2, sched_yield.2, select.2, semctl.2, semget.2, semop.2, send.2, sendfile.2, set_thread_area.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setpgid.2, setresuid.2, setreuid.2, setsid.2, setuid.2, setup.2, setxattr.2, shmctl.2, shmget.2, shmop.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, socket.2, socketcall.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, sysctl.2, sysfs.2, sysinfo.2, syslog.2, tee.2, time.2, timerfd_create.2, times.2, tkill.2, truncate.2, umask.2, umount.2, uname.2, unimplemented.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, MB_CUR_MAX.3, MB_LEN_MAX.3, __setfpucw.3, a64l.3, abort.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_cancel.3, aio_error.3, aio_fsync.3, aio_read.3, aio_return.3, aio_suspend.3, aio_write.3, alloca.3, argz_add.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, backtrace.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, btowc.3, btree.3, byteorder.3, bzero.3, cabs.3, cacos.3, cacosh.3, canonicalize_file_name.3, carg.3, casin.3, casinh.3, catan.3, catanh.3, catgets.3, catopen.3, cbrt.3, ccos.3, ccosh.3, ceil.3, cerf.3, cexp.3, cexp2.3, cfree.3, cimag.3, clearenv.3, clock.3, clock_getcpuclockid.3, clog.3, clog10.3, clog2.3, closedir.3, cmsg.3, confstr.3, conj.3, copysign.3, cos.3, cosh.3, cpow.3, cproj.3, creal.3, crypt.3, csin.3, csinh.3, csqrt.3, ctan.3, ctanh.3, ctermid.3, ctime.3, daemon.3, dbopen.3, des_crypt.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dlopen.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, encrypt.3, end.3, endian.3, envz_add.3, erf.3, erfc.3, err.3, errno.3, error.3, ether_aton.3, euidaccess.3, exec.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, fclose.3, fcloseall.3, fdim.3, fenv.3, ferror.3, fexecve.3, fflush.3, ffs.3, fgetgrent.3, fgetpwent.3, fgetwc.3, fgetws.3, finite.3, flockfile.3, floor.3, fma.3, fmax.3, fmemopen.3, fmin.3, fmod.3, fmtmsg.3, fnmatch.3, fopen.3, fpathconf.3, fpclassify.3, fpurge.3, fputwc.3, fputws.3, fread.3, frexp.3, fseek.3, fseeko.3, ftime.3, ftok.3, fts.3, ftw.3, futimes.3, fwide.3, gamma.3, gcvt.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getcontext.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getenv.3, getfsent.3, getgrent.3, getgrent_r.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getipnodebyname.3, getline.3, getloadavg.3, getlogin.3, getmntent.3, getnameinfo.3, getnetent.3, getnetent_r.3, getopt.3, getpass.3, getprotoent.3, getprotoent_r.3, getpt.3, getpw.3, getpwent.3, getpwent_r.3, getpwnam.3, getrpcent.3, getrpcent_r.3, getrpcport.3, gets.3, getservent.3, getservent_r.3, getspnam.3, getttyent.3, getumask.3, getusershell.3, getutent.3, getw.3, getwchar.3, glob.3, grantpt.3, gsignal.3, hash.3, hsearch.3, hypot.3, iconv.3, iconv_close.3, iconv_open.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, isgreater.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, j0.3, key_setsecret.3, ldexp.3, lgamma.3, lio_listio.3, localeconv.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, login.3, longjmp.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, malloc.3, malloc_hook.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, mempcpy.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mpool.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, nan.3, netlink.3, nextafter.3, nl_langinfo.3, offsetof.3, on_exit.3, opendir.3, openpty.3, perror.3, popen.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, printf.3, profil.3, program_invocation_name.3, psignal.3, pthread_kill_other_threads_np.3, ptsname.3, putenv.3, putgrent.3, putpwent.3, puts.3, putwchar.3, qecvt.3, qsort.3, queue.3, raise.3, rand.3, random.3, random_r.3, rcmd.3, re_comp.3, readdir.3, realpath.3, recno.3, regex.3, remainder.3, remove.3, remquo.3, resolver.3, rewinddir.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, rtime.3, rtnetlink.3, scalb.3, scalbln.3, scandir.3, scandirat.3, scanf.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, setlocale.3, setlogmask.3, setnetgrent.3, shm_open.3, siginterrupt.3, signbit.3, significand.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sin.3, sincos.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdarg.3, stdin.3, stdio.3, stdio_ext.3, stpcpy.3, stpncpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfmon.3, strfry.3, strftime.3, string.3, strlen.3, strnlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtod.3, strtoimax.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, towctrans.3, towlower.3, towupper.3, trunc.3, tsearch.3, ttyname.3, ttyslot.3, tzset.3, ualarm.3, ulimit.3, ungetwc.3, unlocked_stdio.3, unlockpt.3, updwtmp.3, usleep.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstoimax.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wordexp.3, wprintf.3, xcrypt.3, xdr.3, y0.3, cciss.4, console.4, console_codes.4, console_ioctl.4, dsp56k.4, fd.4, full.4, hd.4, hpsa.4, initrd.4, intro.4, lp.4, mem.4, mouse.4, null.4, pts.4, ram.4, random.4, rtc.4, sk98lin.4, st.4, tty.4, ttyS.4, tty_ioctl.4, vcs.4, wavelan.4, acct.5, charmap.5, dir_colors.5, filesystems.5, ftpusers.5, group.5, host.conf.5, hosts.5, hosts.equiv.5, intro.5, issue.5, locale.5, motd.5, networks.5, nologin.5, nscd.conf.5, passwd.5, proc.5, protocols.5, resolv.conf.5, rpc.5, securetty.5, services.5, shells.5, termcap.5, ttytype.5, utmp.5, armscii-8.7, arp.7, ascii.7, bootparam.7, capabilities.7, charsets.7, complex.7, cp1251.7, credentials.7, ddp.7, environ.7, epoll.7, fifo.7, futex.7, glob.7, hier.7, icmp.7, inotify.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, locale.7, mailaddr.7, man.7, mq_overview.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, raw.7, regex.7, rtld-audit.7, rtnetlink.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, socket.7, standards.7, suffixes.7, svipc.7, tcp.7, termio.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, nscd.8, sync.8, tzselect.8, zdump.8, zic.8: Global fix: remove unneeded double quotes in .SH headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:01:36 +00:00
|
|
|
.SH RETURN VALUE
|
2004-11-03 13:51:07 +00:00
|
|
|
On success,
|
2005-10-19 06:54:38 +00:00
|
|
|
.BR select ()
|
2004-11-03 13:51:07 +00:00
|
|
|
and
|
2005-10-19 06:54:38 +00:00
|
|
|
.BR pselect ()
|
2006-04-20 21:21:42 +00:00
|
|
|
return the number of file descriptors contained in the three returned
|
|
|
|
descriptor sets (that is, the total number of bits that are set in
|
2004-11-03 13:51:07 +00:00
|
|
|
.IR readfds ,
|
|
|
|
.IR writefds ,
|
|
|
|
.IR exceptfds )
|
|
|
|
which may be zero if the timeout expires before anything interesting happens.
|
|
|
|
On error, \-1 is returned, and
|
|
|
|
.I errno
|
2014-01-24 09:24:26 +00:00
|
|
|
is set to indicate the error;
|
|
|
|
the file descriptor sets are unmodified,
|
|
|
|
and
|
2004-11-03 13:51:07 +00:00
|
|
|
.I timeout
|
2014-01-24 09:24:26 +00:00
|
|
|
becomes undefined.
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH ERRORS
|
|
|
|
.TP
|
|
|
|
.B EBADF
|
|
|
|
An invalid file descriptor was given in one of the sets.
|
2007-04-12 22:42:49 +00:00
|
|
|
(Perhaps a file descriptor that was already closed,
|
2006-05-13 06:08:41 +00:00
|
|
|
or one on which an error has occurred.)
|
2004-11-03 13:51:07 +00:00
|
|
|
.TP
|
|
|
|
.B EINTR
|
2008-07-04 15:50:36 +00:00
|
|
|
A signal was caught; see
|
|
|
|
.BR signal (7).
|
2004-11-03 13:51:07 +00:00
|
|
|
.TP
|
|
|
|
.B EINVAL
|
2006-05-13 06:08:41 +00:00
|
|
|
.I nfds
|
2015-01-13 09:28:34 +00:00
|
|
|
is negative or exceeds the
|
|
|
|
.BR RLIMIT_NOFILE
|
|
|
|
resource limit (see
|
|
|
|
.BR getrlimit (2)).
|
|
|
|
.TP
|
|
|
|
.B EINVAL
|
|
|
|
the value contained within
|
2004-11-03 13:51:07 +00:00
|
|
|
.I timeout
|
|
|
|
is invalid.
|
|
|
|
.TP
|
|
|
|
.B ENOMEM
|
2006-05-13 06:08:41 +00:00
|
|
|
unable to allocate memory for internal tables.
|
2007-05-18 16:06:42 +00:00
|
|
|
.SH VERSIONS
|
|
|
|
.BR pselect ()
|
|
|
|
was added to Linux in kernel 2.6.16.
|
|
|
|
Prior to this,
|
|
|
|
.BR pselect ()
|
|
|
|
was emulated in glibc (but see BUGS).
|
getent.1, intro.1, time.1, _exit.2, _syscall.2, accept.2, access.2, acct.2, adjtimex.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bdflush.2, bind.2, brk.2, cacheflush.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, clone.2, close.2, connect.2, create_module.2, delete_module.2, dup.2, epoll_create.2, epoll_ctl.2, epoll_wait.2, eventfd.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, flock.2, fork.2, fstatat.2, fsync.2, futex.2, futimesat.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getitimer.2, getpagesize.2, getpeername.2, getpid.2, getpriority.2, getresuid.2, getrlimit.2, getrusage.2, getsid.2, getsockname.2, getsockopt.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, getxattr.2, idle.2, init_module.2, inotify_add_watch.2, inotify_init.2, inotify_rm_watch.2, intro.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, ioprio_set.2, ipc.2, kcmp.2, kill.2, killpg.2, link.2, linkat.2, listen.2, listxattr.2, llseek.2, lookup_dcookie.2, lseek.2, madvise.2, migrate_pages.2, mincore.2, mkdir.2, mkdirat.2, mknod.2, mknodat.2, mlock.2, mmap.2, mmap2.2, modify_ldt.2, mount.2, move_pages.2, mprotect.2, mq_getsetattr.2, mremap.2, msgctl.2, msgget.2, msgop.2, msync.2, nanosleep.2, nfsservctl.2, nice.2, open.2, openat.2, outb.2, pause.2, pciconfig_read.2, perf_event_open.2, perfmonctl.2, personality.2, pipe.2, pivot_root.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, ptrace.2, query_module.2, quotactl.2, read.2, readahead.2, readdir.2, readlink.2, readlinkat.2, readv.2, reboot.2, recv.2, remap_file_pages.2, removexattr.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, sched_get_priority_max.2, sched_rr_get_interval.2, sched_setaffinity.2, sched_setparam.2, sched_setscheduler.2, sched_yield.2, select.2, semctl.2, semget.2, semop.2, send.2, sendfile.2, set_thread_area.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setpgid.2, setresuid.2, setreuid.2, setsid.2, setuid.2, setup.2, setxattr.2, shmctl.2, shmget.2, shmop.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, socket.2, socketcall.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, sysctl.2, sysfs.2, sysinfo.2, syslog.2, tee.2, time.2, timerfd_create.2, times.2, tkill.2, truncate.2, umask.2, umount.2, uname.2, unimplemented.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, MB_CUR_MAX.3, MB_LEN_MAX.3, __setfpucw.3, a64l.3, abort.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_cancel.3, aio_error.3, aio_fsync.3, aio_read.3, aio_return.3, aio_suspend.3, aio_write.3, alloca.3, argz_add.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, backtrace.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, btowc.3, btree.3, byteorder.3, bzero.3, cabs.3, cacos.3, cacosh.3, canonicalize_file_name.3, carg.3, casin.3, casinh.3, catan.3, catanh.3, catgets.3, catopen.3, cbrt.3, ccos.3, ccosh.3, ceil.3, cerf.3, cexp.3, cexp2.3, cfree.3, cimag.3, clearenv.3, clock.3, clock_getcpuclockid.3, clog.3, clog10.3, clog2.3, closedir.3, cmsg.3, confstr.3, conj.3, copysign.3, cos.3, cosh.3, cpow.3, cproj.3, creal.3, crypt.3, csin.3, csinh.3, csqrt.3, ctan.3, ctanh.3, ctermid.3, ctime.3, daemon.3, dbopen.3, des_crypt.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dlopen.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, encrypt.3, end.3, endian.3, envz_add.3, erf.3, erfc.3, err.3, errno.3, error.3, ether_aton.3, euidaccess.3, exec.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, fclose.3, fcloseall.3, fdim.3, fenv.3, ferror.3, fexecve.3, fflush.3, ffs.3, fgetgrent.3, fgetpwent.3, fgetwc.3, fgetws.3, finite.3, flockfile.3, floor.3, fma.3, fmax.3, fmemopen.3, fmin.3, fmod.3, fmtmsg.3, fnmatch.3, fopen.3, fpathconf.3, fpclassify.3, fpurge.3, fputwc.3, fputws.3, fread.3, frexp.3, fseek.3, fseeko.3, ftime.3, ftok.3, fts.3, ftw.3, futimes.3, fwide.3, gamma.3, gcvt.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getcontext.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getenv.3, getfsent.3, getgrent.3, getgrent_r.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getipnodebyname.3, getline.3, getloadavg.3, getlogin.3, getmntent.3, getnameinfo.3, getnetent.3, getnetent_r.3, getopt.3, getpass.3, getprotoent.3, getprotoent_r.3, getpt.3, getpw.3, getpwent.3, getpwent_r.3, getpwnam.3, getrpcent.3, getrpcent_r.3, getrpcport.3, gets.3, getservent.3, getservent_r.3, getspnam.3, getttyent.3, getumask.3, getusershell.3, getutent.3, getw.3, getwchar.3, glob.3, grantpt.3, gsignal.3, hash.3, hsearch.3, hypot.3, iconv.3, iconv_close.3, iconv_open.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, isgreater.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, j0.3, key_setsecret.3, ldexp.3, lgamma.3, lio_listio.3, localeconv.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, login.3, longjmp.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, malloc.3, malloc_hook.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, mempcpy.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mpool.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, nan.3, netlink.3, nextafter.3, nl_langinfo.3, offsetof.3, on_exit.3, opendir.3, openpty.3, perror.3, popen.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, printf.3, profil.3, program_invocation_name.3, psignal.3, pthread_kill_other_threads_np.3, ptsname.3, putenv.3, putgrent.3, putpwent.3, puts.3, putwchar.3, qecvt.3, qsort.3, queue.3, raise.3, rand.3, random.3, random_r.3, rcmd.3, re_comp.3, readdir.3, realpath.3, recno.3, regex.3, remainder.3, remove.3, remquo.3, resolver.3, rewinddir.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, rtime.3, rtnetlink.3, scalb.3, scalbln.3, scandir.3, scandirat.3, scanf.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, setlocale.3, setlogmask.3, setnetgrent.3, shm_open.3, siginterrupt.3, signbit.3, significand.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sin.3, sincos.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdarg.3, stdin.3, stdio.3, stdio_ext.3, stpcpy.3, stpncpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfmon.3, strfry.3, strftime.3, string.3, strlen.3, strnlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtod.3, strtoimax.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, towctrans.3, towlower.3, towupper.3, trunc.3, tsearch.3, ttyname.3, ttyslot.3, tzset.3, ualarm.3, ulimit.3, ungetwc.3, unlocked_stdio.3, unlockpt.3, updwtmp.3, usleep.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstoimax.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wordexp.3, wprintf.3, xcrypt.3, xdr.3, y0.3, cciss.4, console.4, console_codes.4, console_ioctl.4, dsp56k.4, fd.4, full.4, hd.4, hpsa.4, initrd.4, intro.4, lp.4, mem.4, mouse.4, null.4, pts.4, ram.4, random.4, rtc.4, sk98lin.4, st.4, tty.4, ttyS.4, tty_ioctl.4, vcs.4, wavelan.4, acct.5, charmap.5, dir_colors.5, filesystems.5, ftpusers.5, group.5, host.conf.5, hosts.5, hosts.equiv.5, intro.5, issue.5, locale.5, motd.5, networks.5, nologin.5, nscd.conf.5, passwd.5, proc.5, protocols.5, resolv.conf.5, rpc.5, securetty.5, services.5, shells.5, termcap.5, ttytype.5, utmp.5, armscii-8.7, arp.7, ascii.7, bootparam.7, capabilities.7, charsets.7, complex.7, cp1251.7, credentials.7, ddp.7, environ.7, epoll.7, fifo.7, futex.7, glob.7, hier.7, icmp.7, inotify.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, locale.7, mailaddr.7, man.7, mq_overview.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, raw.7, regex.7, rtld-audit.7, rtnetlink.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, socket.7, standards.7, suffixes.7, svipc.7, tcp.7, termio.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, nscd.8, sync.8, tzselect.8, zdump.8, zic.8: Global fix: remove unneeded double quotes in .SH headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:01:36 +00:00
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.SH CONFORMING TO
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2007-04-12 22:42:49 +00:00
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.BR select ()
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2015-04-18 06:10:32 +00:00
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conforms to POSIX.1-2001, POSIX.1-2008, and
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2007-04-12 22:42:49 +00:00
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4.4BSD
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2006-03-07 02:25:37 +00:00
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.RB ( select ()
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2007-04-12 22:42:49 +00:00
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first appeared in 4.2BSD).
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Generally portable to/from
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2004-11-03 13:51:07 +00:00
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non-BSD systems supporting clones of the BSD socket layer (including
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clone.2, execve.2, getpriority.2, ipc.2, kcmp.2, killpg.2, msgctl.2, msgget.2, msgop.2, select.2, semctl.2, semget.2, semop.2, setpgid.2, shmctl.2, shmget.2, shmop.2, sigaction.2, signal.2, socket.2, socketpair.2, syscalls.2, umask.2, unshare.2: ffix: Don't allow line break inside "System V"
2014-04-28 07:36:03 +00:00
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System\ V variants).
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However, note that the System\ V variant typically
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2004-11-03 13:51:07 +00:00
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sets the timeout variable before exit, but the BSD variant does not.
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.PP
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.BR pselect ()
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is defined in POSIX.1g, and in
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2015-04-18 06:10:32 +00:00
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POSIX.1-2001 and POSIX.1-2008.
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.SH NOTES
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An
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.I fd_set
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is a fixed size buffer.
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Executing
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.BR FD_CLR ()
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or
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2006-04-20 21:21:42 +00:00
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.BR FD_SET ()
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with a value of
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.I fd
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that is negative or is equal to or larger than
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.B FD_SETSIZE
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will result
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in undefined behavior.
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Moreover, POSIX requires
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.I fd
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to be a valid file descriptor.
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Concerning the types involved, the classical situation is that
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2006-04-20 21:21:42 +00:00
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the two fields of a
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2007-04-12 22:42:49 +00:00
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.I timeval
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2007-06-25 10:03:10 +00:00
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structure are typed as
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.I long
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(as shown above), and the structure is defined in
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2004-11-03 13:51:07 +00:00
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.IR <sys/time.h> .
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2015-04-18 06:10:32 +00:00
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The POSIX.1 situation is
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2004-11-03 13:51:07 +00:00
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2007-12-19 06:57:44 +00:00
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.in +4n
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2004-11-03 13:51:07 +00:00
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.nf
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struct timeval {
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time_t tv_sec; /* seconds */
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suseconds_t tv_usec; /* microseconds */
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};
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.fi
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2007-12-19 05:53:30 +00:00
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.in
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2004-11-03 13:51:07 +00:00
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2006-04-20 21:21:42 +00:00
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where the structure is defined in
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2004-11-03 13:51:07 +00:00
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.I <sys/select.h>
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2007-04-12 22:42:49 +00:00
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and the data types
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.I time_t
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and
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.I suseconds_t
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2006-04-20 21:21:42 +00:00
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are defined in
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2004-11-03 13:51:07 +00:00
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.IR <sys/types.h> .
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.LP
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Concerning prototypes, the classical situation is that one should
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include
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.I <time.h>
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for
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2005-10-19 06:54:38 +00:00
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.BR select ().
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2015-04-18 06:10:32 +00:00
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The POSIX.1 situation is that one should include
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2004-11-03 13:51:07 +00:00
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.I <sys/select.h>
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for
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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and
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2005-10-19 06:54:38 +00:00
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.BR pselect ().
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2008-12-05 20:41:42 +00:00
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2014-06-29 08:11:53 +00:00
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Under glibc 2.0,
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.I <sys/select.h>
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gives the wrong prototype for
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2008-12-05 20:41:42 +00:00
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.BR pselect ().
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2014-06-29 08:12:22 +00:00
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Under glibc 2.1 to 2.2.1, it gives
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2004-11-03 13:51:07 +00:00
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when
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.B _GNU_SOURCE
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2008-12-05 20:41:42 +00:00
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is defined.
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2014-06-29 08:12:22 +00:00
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Since glibc 2.2.2, the requirements are as shown in the SYNOPSIS.
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2012-08-17 06:27:58 +00:00
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.SS Multithreaded applications
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If a file descriptor being monitored by
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.BR select ()
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is closed in another thread, the result is unspecified.
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On some UNIX systems,
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.BR select ()
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unblocks and returns, with an indication that the file descriptor is ready
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(a subsequent I/O operation will likely fail with an error,
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unless another the file descriptor reopened between the time
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.BR select ()
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returned and the I/O operations was performed).
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On Linux (and some other systems),
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closing the file descriptor in another thread has no effect on
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.BR select ().
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In summary, any application that relies on a particular behavior
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in this scenario must be considered buggy.
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2014-05-15 20:15:29 +00:00
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.\"
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_exit.2, access.2, brk.2, chmod.2, clone.2, epoll_wait.2, eventfd.2, fork.2, getgroups.2, gethostname.2, getpid.2, getpriority.2, killpg.2, mmap.2, poll.2, posix_fadvise.2, pread.2, ptrace.2, readv.2, sched_setaffinity.2, select.2, seteuid.2, setgid.2, setresuid.2, setreuid.2, setuid.2, sigaction.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, stat.2, timer_create.2, uname.2, wait.2, wait4.2, mq_notify.3, mq_open.3, sigqueue.3, man-pages.7: Remove "ABI" from "C library/kernel ABI differences" subheadings
The "ABI" doesn't really convey anything significant in
the title. These subsections are about describing differences
between the kernel and (g)libc interfaces.
Reported-by: Andries E. Brouwer <Andries.Brouwer@cwi.nl>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2015-05-08 11:08:00 +00:00
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.SS C library/kernel differences
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2012-05-02 03:36:05 +00:00
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The
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2006-03-07 22:38:11 +00:00
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.BR pselect ()
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2012-05-02 03:36:05 +00:00
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interface described in this page is implemented by glibc.
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The underlying Linux system call is named
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.BR pselect6 ().
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2012-06-07 12:21:16 +00:00
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This system call has somewhat different behavior from the glibc
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2012-05-02 03:36:05 +00:00
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wrapper function.
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The Linux
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.BR pselect6 ()
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2007-04-12 22:42:49 +00:00
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system call modifies its
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.I timeout
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2006-03-15 10:27:09 +00:00
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argument.
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2007-06-08 09:56:56 +00:00
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However, the glibc wrapper function hides this behavior
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2006-03-07 22:38:11 +00:00
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by using a local variable for the timeout argument that
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is passed to the system call.
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2007-04-12 22:42:49 +00:00
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Thus, the glibc
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2006-03-07 22:38:11 +00:00
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.BR pselect ()
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2012-04-11 17:44:52 +00:00
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function does not modify its
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.I timeout
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argument;
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2007-06-08 09:56:56 +00:00
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this is the behavior required by POSIX.1-2001.
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2012-05-02 03:36:05 +00:00
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The final argument of the
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2012-06-07 13:18:51 +00:00
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.BR pselect6 ()
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2012-05-10 20:13:04 +00:00
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system call is not a
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2012-05-02 03:36:05 +00:00
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.I "sigset_t\ *"
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pointer, but is instead a structure of the form:
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.in +4
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.nf
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struct {
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const sigset_t *ss; /* Pointer to signal set */
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size_t ss_len; /* Size (in bytes) of object pointed
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to by 'ss' */
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};
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.fi
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.in
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This allows the system call to obtain both
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a pointer to the signal set and its size,
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while allowing for the fact that most architectures
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support a maximum of 6 arguments to a system call.
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2004-11-03 13:51:07 +00:00
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.SH BUGS
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2006-03-07 02:25:37 +00:00
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Glibc 2.0 provided a version of
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2005-10-19 06:54:38 +00:00
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.BR pselect ()
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2007-04-12 22:42:49 +00:00
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that did not take a
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.I sigmask
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2006-03-07 02:25:37 +00:00
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argument.
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2010-08-31 04:59:47 +00:00
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Starting with version 2.1, glibc provided an emulation of
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2007-04-12 22:42:49 +00:00
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.BR pselect ()
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2010-08-31 04:59:47 +00:00
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that was implemented using
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2006-03-07 02:25:37 +00:00
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.BR sigprocmask (2)
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and
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.BR select ().
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2010-08-31 04:59:47 +00:00
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This implementation remained vulnerable to the very race condition that
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2006-03-07 02:25:37 +00:00
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.BR pselect ()
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was designed to prevent.
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2010-08-31 04:59:47 +00:00
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Modern versions of glibc use the (race-free)
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.BR pselect ()
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system call on kernels where it is provided.
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2006-03-07 02:25:37 +00:00
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On systems that lack
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2008-08-20 19:45:18 +00:00
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.BR pselect (),
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2007-04-12 22:42:49 +00:00
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reliable (and more portable) signal trapping can be achieved
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2012-05-02 03:42:40 +00:00
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using the self-pipe trick.
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In this technique,
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a signal handler writes a byte to a pipe whose other end
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2007-04-12 22:42:49 +00:00
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is monitored by
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2006-03-07 02:25:37 +00:00
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.BR select ()
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2012-05-02 03:42:40 +00:00
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in the main program.
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(To avoid possibly blocking when writing to a pipe that may be full
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or reading from a pipe that may be empty,
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nonblocking I/O is used when reading from and writing to the pipe.)
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2004-11-03 13:51:07 +00:00
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Under Linux,
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2005-10-19 06:54:38 +00:00
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.BR select ()
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2004-11-03 13:51:07 +00:00
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may report a socket file descriptor as "ready for reading", while
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2007-04-12 22:42:49 +00:00
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nevertheless a subsequent read blocks.
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This could for example
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2004-11-03 13:51:07 +00:00
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happen when data has arrived but upon examination has wrong
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2007-04-12 22:42:49 +00:00
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checksum and is discarded.
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There may be other circumstances
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2006-03-15 10:27:09 +00:00
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in which a file descriptor is spuriously reported as ready.
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2004-11-03 13:51:07 +00:00
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.\" Stevens discusses a case where accept can block after select
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.\" returns successfully because of an intervening RST from the client.
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2007-06-22 17:16:20 +00:00
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Thus it may be safer to use
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.B O_NONBLOCK
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on sockets that should not block.
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2004-11-03 13:51:07 +00:00
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.\" Maybe the kernel should have returned EIO in such a situation?
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2007-06-16 10:46:33 +00:00
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On Linux,
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.BR select ()
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also modifies
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.I timeout
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if the call is interrupted by a signal handler (i.e., the
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.B EINTR
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error return).
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2015-04-18 06:10:32 +00:00
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This is not permitted by POSIX.1.
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2007-06-16 10:46:33 +00:00
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The Linux
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2007-11-24 10:10:39 +00:00
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.BR pselect ()
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2007-06-16 10:46:33 +00:00
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system call has the same behavior,
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but the glibc wrapper hides this behavior by internally copying the
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.I timeout
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to a local variable and passing that variable to the system call.
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2007-05-19 04:30:20 +00:00
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.SH EXAMPLE
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.nf
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#include <stdio.h>
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2007-09-10 02:44:09 +00:00
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#include <stdlib.h>
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2007-05-19 04:30:20 +00:00
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#include <sys/time.h>
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#include <sys/types.h>
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#include <unistd.h>
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int
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main(void)
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{
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fd_set rfds;
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struct timeval tv;
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int retval;
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/* Watch stdin (fd 0) to see when it has input. */
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FD_ZERO(&rfds);
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FD_SET(0, &rfds);
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/* Wait up to five seconds. */
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tv.tv_sec = 5;
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tv.tv_usec = 0;
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retval = select(1, &rfds, NULL, NULL, &tv);
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/* Don't rely on the value of tv now! */
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if (retval == \-1)
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perror("select()");
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else if (retval)
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printf("Data is available now.\\n");
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/* FD_ISSET(0, &rfds) will be true. */
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else
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printf("No data within five seconds.\\n");
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exit(EXIT_SUCCESS);
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}
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.fi
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getent.1, intro.1, time.1, _exit.2, _syscall.2, accept.2, access.2, acct.2, adjtimex.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bdflush.2, bind.2, brk.2, cacheflush.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, clone.2, close.2, connect.2, create_module.2, delete_module.2, dup.2, epoll_create.2, epoll_ctl.2, epoll_wait.2, eventfd.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, flock.2, fork.2, fstatat.2, fsync.2, futex.2, futimesat.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getitimer.2, getpagesize.2, getpeername.2, getpid.2, getpriority.2, getresuid.2, getrlimit.2, getrusage.2, getsid.2, getsockname.2, getsockopt.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, getxattr.2, idle.2, init_module.2, inotify_add_watch.2, inotify_init.2, inotify_rm_watch.2, intro.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, ioprio_set.2, ipc.2, kcmp.2, kill.2, killpg.2, link.2, linkat.2, listen.2, listxattr.2, llseek.2, lookup_dcookie.2, lseek.2, madvise.2, migrate_pages.2, mincore.2, mkdir.2, mkdirat.2, mknod.2, mknodat.2, mlock.2, mmap.2, mmap2.2, modify_ldt.2, mount.2, move_pages.2, mprotect.2, mq_getsetattr.2, mremap.2, msgctl.2, msgget.2, msgop.2, msync.2, nanosleep.2, nfsservctl.2, nice.2, open.2, openat.2, outb.2, pause.2, pciconfig_read.2, perf_event_open.2, perfmonctl.2, personality.2, pipe.2, pivot_root.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, ptrace.2, query_module.2, quotactl.2, read.2, readahead.2, readdir.2, readlink.2, readlinkat.2, readv.2, reboot.2, recv.2, remap_file_pages.2, removexattr.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, sched_get_priority_max.2, sched_rr_get_interval.2, sched_setaffinity.2, sched_setparam.2, sched_setscheduler.2, sched_yield.2, select.2, semctl.2, semget.2, semop.2, send.2, sendfile.2, set_thread_area.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setpgid.2, setresuid.2, setreuid.2, setsid.2, setuid.2, setup.2, setxattr.2, shmctl.2, shmget.2, shmop.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, socket.2, socketcall.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, sysctl.2, sysfs.2, sysinfo.2, syslog.2, tee.2, time.2, timerfd_create.2, times.2, tkill.2, truncate.2, umask.2, umount.2, uname.2, unimplemented.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, MB_CUR_MAX.3, MB_LEN_MAX.3, __setfpucw.3, a64l.3, abort.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_cancel.3, aio_error.3, aio_fsync.3, aio_read.3, aio_return.3, aio_suspend.3, aio_write.3, alloca.3, argz_add.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, backtrace.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, btowc.3, btree.3, byteorder.3, bzero.3, cabs.3, cacos.3, cacosh.3, canonicalize_file_name.3, carg.3, casin.3, casinh.3, catan.3, catanh.3, catgets.3, catopen.3, cbrt.3, ccos.3, ccosh.3, ceil.3, cerf.3, cexp.3, cexp2.3, cfree.3, cimag.3, clearenv.3, clock.3, clock_getcpuclockid.3, clog.3, clog10.3, clog2.3, closedir.3, cmsg.3, confstr.3, conj.3, copysign.3, cos.3, cosh.3, cpow.3, cproj.3, creal.3, crypt.3, csin.3, csinh.3, csqrt.3, ctan.3, ctanh.3, ctermid.3, ctime.3, daemon.3, dbopen.3, des_crypt.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dlopen.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, encrypt.3, end.3, endian.3, envz_add.3, erf.3, erfc.3, err.3, errno.3, error.3, ether_aton.3, euidaccess.3, exec.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, 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glob.3, grantpt.3, gsignal.3, hash.3, hsearch.3, hypot.3, iconv.3, iconv_close.3, iconv_open.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, isgreater.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, j0.3, key_setsecret.3, ldexp.3, lgamma.3, lio_listio.3, localeconv.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, login.3, longjmp.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, malloc.3, malloc_hook.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, mempcpy.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mpool.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, nan.3, netlink.3, nextafter.3, nl_langinfo.3, offsetof.3, on_exit.3, opendir.3, openpty.3, perror.3, popen.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, printf.3, profil.3, program_invocation_name.3, psignal.3, pthread_kill_other_threads_np.3, ptsname.3, putenv.3, putgrent.3, putpwent.3, puts.3, putwchar.3, qecvt.3, qsort.3, queue.3, raise.3, rand.3, random.3, random_r.3, rcmd.3, re_comp.3, readdir.3, realpath.3, recno.3, regex.3, remainder.3, remove.3, remquo.3, resolver.3, rewinddir.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, rtime.3, rtnetlink.3, scalb.3, scalbln.3, scandir.3, scandirat.3, scanf.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, setlocale.3, setlogmask.3, setnetgrent.3, shm_open.3, siginterrupt.3, signbit.3, significand.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sin.3, sincos.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdarg.3, stdin.3, stdio.3, stdio_ext.3, stpcpy.3, stpncpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfmon.3, strfry.3, strftime.3, string.3, strlen.3, strnlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtod.3, strtoimax.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, towctrans.3, towlower.3, towupper.3, trunc.3, tsearch.3, ttyname.3, ttyslot.3, tzset.3, ualarm.3, ulimit.3, ungetwc.3, unlocked_stdio.3, unlockpt.3, updwtmp.3, usleep.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstoimax.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wordexp.3, wprintf.3, xcrypt.3, xdr.3, y0.3, cciss.4, console.4, console_codes.4, console_ioctl.4, dsp56k.4, fd.4, full.4, hd.4, hpsa.4, initrd.4, intro.4, lp.4, mem.4, mouse.4, null.4, pts.4, ram.4, random.4, rtc.4, sk98lin.4, st.4, tty.4, ttyS.4, tty_ioctl.4, vcs.4, wavelan.4, acct.5, charmap.5, dir_colors.5, filesystems.5, ftpusers.5, group.5, host.conf.5, hosts.5, hosts.equiv.5, intro.5, issue.5, locale.5, motd.5, networks.5, nologin.5, nscd.conf.5, passwd.5, proc.5, protocols.5, resolv.conf.5, rpc.5, securetty.5, services.5, shells.5, termcap.5, ttytype.5, utmp.5, armscii-8.7, arp.7, ascii.7, bootparam.7, capabilities.7, charsets.7, complex.7, cp1251.7, credentials.7, ddp.7, environ.7, epoll.7, fifo.7, futex.7, glob.7, hier.7, icmp.7, inotify.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, locale.7, mailaddr.7, man.7, mq_overview.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, raw.7, regex.7, rtld-audit.7, rtnetlink.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, socket.7, standards.7, suffixes.7, svipc.7, tcp.7, termio.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, nscd.8, sync.8, tzselect.8, zdump.8, zic.8: Global fix: remove unneeded double quotes in .SH headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:01:36 +00:00
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.SH SEE ALSO
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2004-11-03 13:51:07 +00:00
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.BR accept (2),
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.BR connect (2),
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.BR poll (2),
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.BR read (2),
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.BR recv (2),
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2014-12-12 14:53:02 +00:00
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.BR restart_syscall (2),
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2004-11-03 13:51:07 +00:00
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.BR send (2),
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.BR sigprocmask (2),
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2006-04-21 06:49:34 +00:00
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.BR write (2),
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2008-06-23 08:48:25 +00:00
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.BR epoll (7),
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.BR time (7)
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arch_prctl.2, fcntl.2, flock.2, get_robust_list.2, getpriority.2, ioprio_set.2, migrate_pages.2, mmap.2, mremap.2, msync.2, sched_get_priority_max.2, sched_rr_get_interval.2, sched_setparam.2, sched_setscheduler.2, sched_yield.2, select.2, socket.2, subpage_prot.2, unshare.2, btree.3, dbopen.3, dl_iterate_phdr.3, dlopen.3, getnameinfo.3, hash.3, lockf.3, netlink.3, recno.3, rpc.3, xdr.3, cciss.4, console_ioctl.4, hpsa.4, initrd.4, msr.4, rtc.4, st.4, hosts.5, services.5, tzfile.5, aio.7, arp.7, capabilities.7, cpuset.7, feature_test_macros.7, futex.7, inotify.7, ip.7, ipv6.7, iso_8859-16.7, iso_8859-2.7, koi8-r.7, math_error.7, netlink.7, packet.7, pthreads.7, raw.7, spufs.7, udplite.7, uri.7, x25.7: Global fix: Various consistency fixes for SEE ALSO
Coauthored-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2012-09-24 07:53:22 +00:00
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For a tutorial with discussion and examples, see
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.BR select_tut (2).
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