2004-11-03 13:51:07 +00:00
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.\" Copyright 1993 Giorgio Ciucci (giorgio@crcc.it)
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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.\" manual page may be incorrect or out-of-date.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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2007-09-20 06:52:22 +00:00
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.\" Modified 2001-11-28, by Michael Kerrisk, <mtk.manpages@gmail.com>
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2004-11-03 13:51:07 +00:00
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.\" Changed data type of proj_id; minor fixes
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.\" aeb: further fixes; added notes.
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.\"
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2007-05-30 05:36:26 +00:00
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.TH FTOK 3 2001-11-28 "GNU" "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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ftok \- convert a pathname and a project identifier to a System V IPC key
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.SH SYNOPSIS
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.nf
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2008-06-18 08:57:49 +00:00
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.B #include <sys/types.h>
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.B #include <sys/ipc.h>
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.fi
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.sp
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.BI "key_t ftok(const char *" pathname ", int " proj_id );
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.SH DESCRIPTION
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The
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2005-10-19 06:54:38 +00:00
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.BR ftok ()
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function uses the identity of the file named by the given
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.I pathname
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(which must refer to an existing, accessible file)
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and the least significant 8 bits of
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.I proj_id
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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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(which must be nonzero) to generate a
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.I key_t
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type System V IPC key, suitable for use with
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.BR msgget (2),
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.BR semget (2),
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or
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.BR shmget (2).
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.LP
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The resulting value is the same for all pathnames that
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name the same file, when the same value of
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.I proj_id
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is used.
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The value returned should be different when the
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2004-11-03 13:51:07 +00:00
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(simultaneously existing) files or the project IDs differ.
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.SH "RETURN VALUE"
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On success the generated
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.I key_t
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value is returned.
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On failure \-1 is returned, with
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.I errno
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indicating the error as for the
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.BR stat (2)
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system call.
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.SH "CONFORMING TO"
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2006-08-03 13:57:30 +00:00
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POSIX.1-2001.
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2004-11-03 13:51:07 +00:00
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.SH NOTES
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2007-07-09 20:43:38 +00:00
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Under libc4 and libc5 (and under SunOS 4.x) the prototype was:
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.sp
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2004-11-03 13:51:07 +00:00
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.RS
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.BI "key_t ftok(char *" pathname ", char " proj_id );
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.RE
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2007-07-09 20:43:38 +00:00
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.PP
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2004-11-03 13:51:07 +00:00
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Today
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.I proj_id
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is an
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2006-02-09 20:24:53 +00:00
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.IR int ,
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2007-04-12 22:42:49 +00:00
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but still only 8 bits are used.
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Typical usage has an ASCII character
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.IR proj_id ,
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2007-06-08 09:56:56 +00:00
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that is why the behavior is said to be undefined when
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2004-11-03 13:51:07 +00:00
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.I proj_id
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is zero.
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.LP
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Of course no guarantee can be given that the resulting
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.I key_t
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is unique.
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Typically, a best effort attempt combines the given
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.I proj_id
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2008-01-09 09:47:31 +00:00
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byte, the lower 16 bits of the inode number, and the
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2007-12-26 08:00:10 +00:00
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lower 8 bits of the device number into a 32-bit result.
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Collisions may easily happen, for example between files on
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.I /dev/hda1
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and files on
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.IR /dev/sda1 .
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.SH "SEE ALSO"
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.BR msgget (2),
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.BR semget (2),
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.BR shmget (2),
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.BR stat (2),
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2006-04-21 03:53:43 +00:00
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.BR svipc (7)
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