man2/getgid.2

   1 .\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .TH getgid 2 (date) "Linux man-pages (unreleased)"
   6 .SH NAME
   7 getgid, getegid \- get group identity
   8 .SH LIBRARY
   9 Standard C library
  10 .RI ( libc ", " \-lc )
  11 .SH SYNOPSIS
  12 .nf
  13 .B #include <unistd.h>
  14 .PP
  15 .B gid_t getgid(void);
  16 .B gid_t getegid(void);
  17 .fi
  18 .SH DESCRIPTION
  19 .BR getgid ()
  20 returns the real group ID of the calling process.
  21 .PP
  22 .BR getegid ()
  23 returns the effective group ID of the calling process.
  24 .SH ERRORS
  25 These functions are always successful
  26 and never modify
  27 .\" https://www.austingroupbugs.net/view.php?id=511
  28 .\" 0000511: getuid and friends should not modify errno
  29 .IR errno .
  30 .SH STANDARDS
  31 POSIX.1-2001, POSIX.1-2008, 4.3BSD.
  32 .SH NOTES
  33 The original Linux
  34 .BR getgid ()
  35 and
  36 .BR getegid ()
  37 system calls supported only 16-bit group IDs.
  38 Subsequently, Linux 2.4 added
  39 .BR getgid32 ()
  40 and
  41 .BR getegid32 (),
  42 supporting 32-bit IDs.
  43 The glibc
  44 .BR getgid ()
  45 and
  46 .BR getegid ()
  47 wrapper functions transparently deal with the variations across kernel versions.
  48 .PP
  49 On Alpha, instead of a pair of
  50 .BR getgid ()
  51 and
  52 .BR getegid ()
  53 system calls, a single
  54 .BR getxgid ()
  55 system call is provided, which returns a pair of real and effective GIDs.
  56 The glibc
  57 .BR getgid ()
  58 and
  59 .BR getegid ()
  60 wrapper functions transparently deal with this.
  61 See
  62 .BR syscall (2)
  63 for details regarding register mapping.
  64 .SH SEE ALSO
  65 .BR getresgid (2),
  66 .BR setgid (2),
  67 .BR setregid (2),
  68 .BR credentials (7)