2004-11-03 13:51:07 +00:00
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.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>.
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.\"
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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.\" manual page may be incorrect or out-of-date.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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.\"
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2008-08-29 15:50:13 +00:00
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.TH FLOCKFILE 3 2008-08-29 "" "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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flockfile, ftrylockfile, funlockfile \- lock FILE for stdio
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.SH SYNOPSIS
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.nf
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.B #include <stdio.h>
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.sp
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.BI "void flockfile(FILE *" filehandle );
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.br
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.BI "int ftrylockfile(FILE *" filehandle );
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.br
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.BI "void funlockfile(FILE *" filehandle );
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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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.ad l
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.sp
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2007-12-23 09:00:11 +00:00
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All functions shown above:
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2010-09-19 04:59:15 +00:00
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.RS 4
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2008-08-29 15:50:13 +00:00
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_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
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_SVID_SOURCE || _POSIX_SOURCE
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2010-09-19 04:59:15 +00:00
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.RE
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2007-07-08 12:11:40 +00:00
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.ad b
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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2007-04-12 22:42:49 +00:00
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The stdio functions are thread-safe.
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This is achieved by assigning
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2007-06-22 19:42:52 +00:00
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to each
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2007-06-22 20:40:07 +00:00
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.I FILE
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intro.1, time.1, adjtimex.2, capget.2, eventfd.2, fcntl.2, getrlimit.2, getsockopt.2, gettimeofday.2, intro.2, ioctl_list.2, ioperm.2, mlock.2, pivot_root.2, poll.2, prctl.2, ptrace.2, sched_setscheduler.2, select_tut.2, semget.2, sigaltstack.2, signalfd.2, sysctl.2, timer_settime.2, timerfd_create.2, wait.2, CPU_SET.3, argz_add.3, assert_perror.3, atexit.3, backtrace.3, bcmp.3, clearenv.3, ctime.3, dl_iterate_phdr.3, dlopen.3, ecvt.3, errno.3, error.3, ether_aton.3, exit.3, fenv.3, ferror.3, finite.3, flockfile.3, fnmatch.3, fpathconf.3, fpclassify.3, ftime.3, ftok.3, ftw.3, fwide.3, getaddrinfo.3, gethostbyname.3, getlogin.3, getnameinfo.3, getnetent.3, getopt.3, getprotoent.3, getrpcent.3, getservent.3, glob.3, hsearch.3, inet.3, isalpha.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, longjmp.3, lsearch.3, malloc.3, matherr.3, mblen.3, mbsinit.3, mbtowc.3, on_exit.3, printf.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_equal.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setschedparam.3, pthread_setschedprio.3, ptsname.3, putenv.3, putgrent.3, raise.3, rcmd.3, regex.3, rexec.3, rpc.3, rpmatch.3, rtnetlink.3, scandir.3, sem_init.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, signbit.3, stdio_ext.3, strtod.3, strtol.3, strtoul.3, system.3, termios.3, timeradd.3, tzset.3, ualarm.3, wctomb.3, xdr.3, st.4, tty_ioctl.4, core.5, elf.5, proc.5, bootparam.7, capabilities.7, icmp.7, ip.7, ipv6.7, math_error.7, mdoc.samples.7, mq_overview.7, pthreads.7, raw.7, regex.7, socket.7, tcp.7, tzselect.8: Global fix: s/non-zero/nonzero/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:40:55 +00:00
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object a lockcount and (if the lockcount is nonzero)
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2004-11-03 13:51:07 +00:00
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an owning thread.
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2007-06-22 19:42:52 +00:00
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For each library call, these functions wait until the
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2007-06-22 20:40:07 +00:00
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.I FILE
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2007-06-22 19:42:52 +00:00
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object
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2004-11-03 13:51:07 +00:00
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is no longer locked by a different thread, then lock it, do the
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requested I/O, and unlock the object again.
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.LP
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(Note: this locking has nothing to do with the file locking done
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by functions like
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.BR flock (2)
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and
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.BR lockf (3).)
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.LP
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All this is invisible to the C-programmer, but there may be two
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2007-04-12 22:42:49 +00:00
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reasons to wish for more detailed control.
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On the one hand, maybe
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2004-11-03 13:51:07 +00:00
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a series of I/O actions by one thread belongs together, and should
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not be interrupted by the I/O of some other thread.
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On the other hand, maybe the locking overhead should be avoided
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for greater efficiency.
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.LP
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2007-06-22 19:42:52 +00:00
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To this end, a thread can explicitly lock the
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2007-06-22 20:40:07 +00:00
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.I FILE
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2007-06-22 19:42:52 +00:00
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object,
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2007-04-12 22:42:49 +00:00
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then do its series of I/O actions, then unlock.
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This prevents
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other threads from coming in between.
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If the reason for doing
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2004-11-03 13:51:07 +00:00
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this was to achieve greater efficiency, one does the I/O with
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accept.2, access.2, acct.2, clock_nanosleep.2, mbind.2, mincore.2, remap_file_pages.2, sched_setscheduler.2, set_mempolicy.2, splice.2, stat.2, syslog.2, timer_create.2, timerfd_create.2, truncate.2, fenv.3, ferror.3, fflush.3, fgetwc.3, fgetws.3, flockfile.3, fputwc.3, fputws.3, fread.3, getopt.3, gets.3, getwchar.3, glob.3, iconv.3, longjmp.3, pow.3, printf.3, puts.3, putwchar.3, regex.3, rpc.3, scanf.3, setjmp.3, termios.3, unlocked_stdio.3, wcswidth.3, hd.4, rtc.4, st.4, core.5, dir_colors.5, elf.5, proc.5, arp.7, ascii.7, boot.7, bootparam.7, charsets.7, futex.7, ip.7, iso_8859-11.7, man-pages.7, man.7, mdoc.samples.7, path_resolution.7, pipe.7, posixoptions.7, unicode.7, unix.7, uri.7, utf-8.7, ld.so.8: s/non-/non/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 17:20:12 +00:00
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the nonlocking versions of the stdio functions: with
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2007-05-12 13:12:02 +00:00
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.BR getc_unlocked (3)
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and
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.BR putc_unlocked (3)
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instead of
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.BR getc (3)
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and
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.BR putc (3).
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2004-11-03 13:51:07 +00:00
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.LP
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2007-05-12 09:06:04 +00:00
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The
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.BR flockfile ()
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2007-12-22 21:40:53 +00:00
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function waits for \fI*filehandle\fP to be
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2004-11-03 13:51:07 +00:00
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no longer locked by a different thread, then makes the
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2007-12-22 21:40:53 +00:00
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current thread owner of \fI*filehandle\fP, and increments
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2004-11-03 13:51:07 +00:00
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the lockcount.
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.LP
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2007-05-12 09:06:04 +00:00
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The
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.BR funlockfile ()
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function decrements the lock count.
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2004-11-03 13:51:07 +00:00
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.LP
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2007-05-12 09:06:04 +00:00
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The
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.BR ftrylockfile ()
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accept.2, connect.2, eventfd.2, flock.2, open.2, posix_fadvise.2, read.2, recv.2, sched_setscheduler.2, select_tut.2, send.2, signalfd.2, splice.2, timerfd_create.2, write.2, flockfile.3, mkfifo.3, mq_notify.3, mq_open.3, pthread_tryjoin_np.3, scanf.3, random.4, ddp.7, epoll.7, fifo.7, ip.7, pipe.7, socket.7, spufs.7: Global fix: s/non-blocking/nonblocking/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:43:10 +00:00
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function is a nonblocking version
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2007-05-12 09:06:04 +00:00
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of
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.BR flockfile ().
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2007-04-12 22:42:49 +00:00
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It does nothing in case some other thread
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2007-12-22 21:40:53 +00:00
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owns \fI*filehandle\fP, and it obtains ownership and increments
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2004-11-03 13:51:07 +00:00
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the lockcount otherwise.
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.SH "RETURN VALUE"
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2007-05-12 09:06:04 +00:00
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The
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.BR ftrylockfile ()
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function returns zero for success
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intro.1, time.1, adjtimex.2, capget.2, eventfd.2, fcntl.2, getrlimit.2, getsockopt.2, gettimeofday.2, intro.2, ioctl_list.2, ioperm.2, mlock.2, pivot_root.2, poll.2, prctl.2, ptrace.2, sched_setscheduler.2, select_tut.2, semget.2, sigaltstack.2, signalfd.2, sysctl.2, timer_settime.2, timerfd_create.2, wait.2, CPU_SET.3, argz_add.3, assert_perror.3, atexit.3, backtrace.3, bcmp.3, clearenv.3, ctime.3, dl_iterate_phdr.3, dlopen.3, ecvt.3, errno.3, error.3, ether_aton.3, exit.3, fenv.3, ferror.3, finite.3, flockfile.3, fnmatch.3, fpathconf.3, fpclassify.3, ftime.3, ftok.3, ftw.3, fwide.3, getaddrinfo.3, gethostbyname.3, getlogin.3, getnameinfo.3, getnetent.3, getopt.3, getprotoent.3, getrpcent.3, getservent.3, glob.3, hsearch.3, inet.3, isalpha.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, longjmp.3, lsearch.3, malloc.3, matherr.3, mblen.3, mbsinit.3, mbtowc.3, on_exit.3, printf.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_equal.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setschedparam.3, pthread_setschedprio.3, ptsname.3, putenv.3, putgrent.3, raise.3, rcmd.3, regex.3, rexec.3, rpc.3, rpmatch.3, rtnetlink.3, scandir.3, sem_init.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, signbit.3, stdio_ext.3, strtod.3, strtol.3, strtoul.3, system.3, termios.3, timeradd.3, tzset.3, ualarm.3, wctomb.3, xdr.3, st.4, tty_ioctl.4, core.5, elf.5, proc.5, bootparam.7, capabilities.7, icmp.7, ip.7, ipv6.7, math_error.7, mdoc.samples.7, mq_overview.7, pthreads.7, raw.7, regex.7, socket.7, tcp.7, tzselect.8: Global fix: s/non-zero/nonzero/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:40:55 +00:00
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(the lock was obtained), and nonzero for failure.
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2004-11-03 13:51:07 +00:00
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.SH ERRORS
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None.
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2007-05-19 04:30:20 +00:00
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.SH "CONFORMING TO"
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POSIX.1-2001.
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2004-11-03 13:51:07 +00:00
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.SH AVAILABILITY
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2007-07-08 16:21:19 +00:00
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These functions are available when
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.B _POSIX_THREAD_SAFE_FUNCTIONS
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2007-04-12 22:42:49 +00:00
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is defined.
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They are in libc since libc 5.1.1 and in glibc
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2004-11-03 13:51:07 +00:00
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since glibc 2.0.
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.SH "SEE ALSO"
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.BR unlocked_stdio (3)
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