2012-02-26 18:47:07 +00:00
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.\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com>
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2012-02-27 01:14:12 +00:00
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.\" with some material from a draft by
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2011-09-09 23:02:43 +00:00
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.\" Stephan Mueller <stephan.mueller@atsec.com>
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.\" in turn based on Andi Kleen's recvmmsg.2 page.
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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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2011-09-09 23:02:43 +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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.\"
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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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.\"
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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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2012-02-27 01:14:12 +00:00
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.\"
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2012-12-15 18:21:40 +00:00
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.TH SENDMMSG 2 2012-12-16 "Linux" "Linux Programmer's Manual"
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2011-09-09 23:02:43 +00:00
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.SH NAME
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sendmmsg \- send multiple messages on a socket
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.SH SYNOPSIS
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.nf
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.B "#define _GNU_SOURCE"
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.BI "#include <sys/socket.h>"
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.BI "int sendmmsg(int " sockfd ", struct mmsghdr *" msgvec \
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", unsigned int " vlen ","
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2012-02-27 01:14:12 +00:00
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.BI " unsigned int " flags ");"
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2011-09-09 23:02:43 +00:00
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.fi
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.SH DESCRIPTION
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2012-02-27 01:14:12 +00:00
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The
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2011-09-09 23:02:43 +00:00
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.BR sendmmsg ()
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system call is an extension of
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.BR sendmsg (2)
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that allows the caller to transmit multiple messages on a socket
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using a single system call.
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(This has performance benefits for some applications.)
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.\" See commit 228e548e602061b08ee8e8966f567c12aa079682
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The
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2012-02-27 01:14:12 +00:00
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.I sockfd
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2011-09-09 23:02:43 +00:00
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argument is the file descriptor of the socket
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on which data is to be transmitted.
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The
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.I msgvec
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argument is a pointer to an array of
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.I mmsghdr
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structures.
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The size of this array is specified in
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.IR vlen .
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The
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.I mmsghdr
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structure is defined in
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.I <sys/socket.h>
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as:
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.in +4n
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.nf
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struct mmsghdr {
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struct msghdr msg_hdr; /* Message header */
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unsigned int msg_len; /* Number of bytes transmitted */
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};
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.fi
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.in
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.PP
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The
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2012-02-27 01:14:12 +00:00
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.I msg_hdr
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2011-09-09 23:02:43 +00:00
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field is a
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.I msghdr
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structure, as described in
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.BR sendmsg (2).
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The
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|
.I msg_len
|
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|
|
field is used to return the number of bytes sent from the message in
|
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|
.IR msg_hdr
|
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|
|
(i.e., the same as the return value from a single
|
|
|
|
.BR sendmsg (2)
|
|
|
|
call).
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The
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|
.I flags
|
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|
|
argument contains flags ORed together.
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|
The flags are the same as for
|
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|
|
.BR sendmsg (2).
|
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|
|
A blocking
|
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|
|
.BR sendmmsg ()
|
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|
|
call blocks until
|
|
|
|
.I vlen
|
|
|
|
messages have been sent.
|
|
|
|
A nonblocking call sends as many messages as possible
|
|
|
|
(up to the limit specified by
|
|
|
|
.IR vlen )
|
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|
|
and returns immediately.
|
|
|
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|
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|
|
On return from
|
|
|
|
.BR sendmmsg (),
|
|
|
|
the
|
|
|
|
.I msg_len
|
|
|
|
fields of successive elements of
|
|
|
|
.IR msgvec
|
|
|
|
are updated to contain the number of bytes transmitted from the corresponding
|
|
|
|
.IR msg_hdr .
|
|
|
|
The return value of the call indicates the number of elements of
|
|
|
|
.I msgvec
|
|
|
|
that have been updated.
|
|
|
|
.SH RETURN VALUE
|
|
|
|
On success,
|
|
|
|
.BR sendmmsg ()
|
|
|
|
returns the number of messages sent from
|
|
|
|
.IR msgvec ;
|
|
|
|
if this is less than
|
|
|
|
.IR vlen ,
|
|
|
|
the caller can retry with a further
|
|
|
|
.BR sendmmsg ()
|
|
|
|
call to send the remaining messages.
|
|
|
|
|
|
|
|
On error, \-1 is returned, and
|
|
|
|
.I errno
|
|
|
|
is set to indicate the error.
|
|
|
|
.SH ERRORS
|
|
|
|
Errors are as for
|
|
|
|
.BR sendmsg (2).
|
|
|
|
An error is returned only if no datagrams could be sent.
|
|
|
|
.\" commit 728ffb86f10873aaf4abd26dde691ee40ae731fe
|
|
|
|
.\" ... only return an error if no datagrams could be sent.
|
|
|
|
.\" If less than the requested number of messages were sent, the application
|
|
|
|
.\" must retry starting at the first failed one and if the problem is
|
|
|
|
.\" persistent the error will be returned.
|
2012-02-27 01:14:12 +00:00
|
|
|
.\"
|
2011-09-09 23:02:43 +00:00
|
|
|
.\" This matches the behaviour of other syscalls like read/write - it
|
|
|
|
.\" is not an error if less than the requested number of elements are sent.
|
|
|
|
.SH VERSIONS
|
|
|
|
The
|
|
|
|
.BR sendmmsg ()
|
|
|
|
system call was added in Linux 3.0.
|
|
|
|
Support in glibc was added in version 2.14.
|
|
|
|
.SH CONFORMING TO
|
|
|
|
.BR sendmmsg ()
|
|
|
|
is Linux-specific.
|
|
|
|
.SH NOTES
|
|
|
|
The value specified in
|
|
|
|
.I vlen
|
|
|
|
is capped to
|
|
|
|
.B UIO_MAXIOV
|
|
|
|
(1024).
|
|
|
|
.\" commit 98382f419f32d2c12d021943b87dea555677144b
|
|
|
|
.\" net: Cap number of elements for sendmmsg
|
2012-02-27 01:14:12 +00:00
|
|
|
.\"
|
2011-09-09 23:02:43 +00:00
|
|
|
.\" To limit the amount of time we can spend in sendmmsg, cap the
|
|
|
|
.\" number of elements to UIO_MAXIOV (currently 1024).
|
|
|
|
.\"
|
|
|
|
.\" For error handling an application using sendmmsg needs to retry at
|
|
|
|
.\" the first unsent message, so capping is simpler and requires less
|
|
|
|
.\" application logic than returning EINVAL.
|
2012-12-15 18:14:27 +00:00
|
|
|
.SH EXAMPLE
|
2012-12-20 17:17:09 +00:00
|
|
|
The example below uses
|
2012-12-15 18:14:27 +00:00
|
|
|
.BR sendmmsg ()
|
2012-12-20 17:17:09 +00:00
|
|
|
to send
|
2012-12-15 18:14:27 +00:00
|
|
|
.I onetwo
|
2012-12-20 17:17:09 +00:00
|
|
|
and
|
2012-12-15 18:14:27 +00:00
|
|
|
.I three
|
2012-12-15 18:21:40 +00:00
|
|
|
in two distinct UDP datagrams using one system call.
|
|
|
|
The contents of the first datagram originates from a pair of buffers.
|
2012-12-15 18:14:27 +00:00
|
|
|
|
|
|
|
.nf
|
|
|
|
#define _GNU_SOURCE
|
2012-12-20 17:17:09 +00:00
|
|
|
#include <netinet/ip.h>
|
2012-12-15 18:14:27 +00:00
|
|
|
#include <stdio.h>
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include <string.h>
|
|
|
|
#include <sys/types.h>
|
|
|
|
#include <sys/socket.h>
|
|
|
|
|
2012-12-20 17:17:09 +00:00
|
|
|
int
|
2012-12-22 21:37:37 +00:00
|
|
|
main(void)
|
2012-12-15 18:14:27 +00:00
|
|
|
{
|
|
|
|
int sockfd;
|
|
|
|
struct sockaddr_in sa;
|
|
|
|
struct mmsghdr msg[2];
|
|
|
|
struct iovec msg1[2], msg2;
|
|
|
|
int retval;
|
|
|
|
|
|
|
|
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
|
|
|
|
if (sockfd == \-1) {
|
|
|
|
perror("socket()");
|
|
|
|
exit(EXIT_FAILURE);
|
|
|
|
}
|
|
|
|
|
2012-12-20 17:17:09 +00:00
|
|
|
sa.sin_family = AF_INET;
|
|
|
|
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
|
|
|
|
sa.sin_port = htons(1234);
|
2012-12-15 18:21:40 +00:00
|
|
|
if (connect(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == \-1) {
|
2012-12-15 18:14:27 +00:00
|
|
|
perror("connect()");
|
|
|
|
exit(EXIT_FAILURE);
|
|
|
|
}
|
|
|
|
|
2012-12-20 17:17:09 +00:00
|
|
|
memset(msg1, 0, sizeof(msg1));
|
2012-12-15 18:14:27 +00:00
|
|
|
msg1[0].iov_base = "one";
|
|
|
|
msg1[0].iov_len = 3;
|
|
|
|
msg1[1].iov_base = "two";
|
|
|
|
msg1[1].iov_len = 3;
|
|
|
|
|
|
|
|
memset(&msg2, 0, sizeof(msg2));
|
|
|
|
msg2.iov_base = "three";
|
|
|
|
msg2.iov_len = 5;
|
|
|
|
|
|
|
|
memset(msg, 0, sizeof(msg));
|
|
|
|
msg[0].msg_hdr.msg_iov = msg1;
|
|
|
|
msg[0].msg_hdr.msg_iovlen = 2;
|
|
|
|
|
|
|
|
msg[1].msg_hdr.msg_iov = &msg2;
|
|
|
|
msg[1].msg_hdr.msg_iovlen = 1;
|
|
|
|
|
|
|
|
retval = sendmmsg(sockfd, msg, 2, 0);
|
2012-12-15 18:21:40 +00:00
|
|
|
if (retval == \-1)
|
2012-12-15 18:14:27 +00:00
|
|
|
perror("sendmmsg()");
|
|
|
|
else
|
|
|
|
printf("%d messages sent\\n", retval);
|
|
|
|
|
|
|
|
exit(0);
|
|
|
|
}
|
|
|
|
.fi
|
2011-09-09 23:02:43 +00:00
|
|
|
.SH SEE ALSO
|
|
|
|
.BR recvmmsg (2),
|
|
|
|
.BR sendmsg (2),
|
|
|
|
.BR socket (2),
|
|
|
|
.BR socket (7)
|