man2/getsid.2

   1 .\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl)
   2 .\" and Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
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  25 .\" Modified Thu Oct 31 14:18:40 1996 by Eric S. Raymond <esr@y\thyrsus.com>
  26 .\" Modified 2001-12-17, aeb
  27 .TH GETSID 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  28 .SH NAME
  29 getsid \- get session ID
  30 .SH SYNOPSIS
  31 .B #include <sys/types.h>
  32 .br
  33 .B #include <unistd.h>
  34 .PP
  35 .BI "pid_t getsid(pid_t" " pid" );
  36 .PP
  37 .in -4n
  38 Feature Test Macro Requirements for glibc (see
  39 .BR feature_test_macros (7)):
  40 .in
  41 .PP
  42 .ad l
  43 .PD 0
  44 .BR getsid ():
  45 .RS 4
  46 _XOPEN_SOURCE\ >=\ 500
  47 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  48 .br
  49     || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
  50 .RE
  51 .PD
  52 .ad
  53 .SH DESCRIPTION
  54 .I getsid(0)
  55 returns the session ID of the calling process.
  56 .BR getsid ()
  57 returns the session ID of the process with process ID
  58 .IR pid .
  59 If
  60 .I pid
  61 is 0,
  62 .BR getsid ()
  63 returns the session ID of the calling process.
  64 .SH RETURN VALUE
  65 On success, a session ID is returned.
  66 On error, \fI(pid_t)\ \-1\fP will be returned, and
  67 .I errno
  68 is set appropriately.
  69 .SH ERRORS
  70 .TP
  71 .B EPERM
  72 A process with process ID
  73 .I pid
  74 exists, but it is not in the same session as the calling process,
  75 and the implementation considers this an error.
  76 .TP
  77 .B ESRCH
  78 No process with process ID
  79 .I pid
  80 was found.
  81 .SH VERSIONS
  82 This system call is available on Linux since version 2.0.
  83 .\" Linux has this system call since Linux 1.3.44.
  84 .\" There is libc support since libc 5.2.19.
  85 .SH CONFORMING TO
  86 POSIX.1-2001, POSIX.1-2008, SVr4.
  87 .SH NOTES
  88 Linux does not return
  89 .BR EPERM .
  90 .PP
  91 See
  92 .BR credentials (7)
  93 for a description of sessions and session IDs.
  94 .SH SEE ALSO
  95 .BR getpgid (2),
  96 .BR setsid (2),
  97 .BR credentials (7)