man2/getresuid.2

   1 .\" Copyright (C) 1997 Andries Brouwer (aeb@cwi.nl)
   2 .\" and Copyright (c) 2007, Michael Kerrisk <mtk.manpages@gmail.com>
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .\" Modified, 2003-05-26, Michael Kerrisk, <mtk.manpages@gmail.com>
   7 .\"
   8 .TH GETRESUID 2 2021-03-22 "Linux" "Linux Programmer's Manual"
   9 .SH NAME
  10 getresuid, getresgid \- get real, effective, and saved user/group IDs
  11 .SH LIBRARY
  12 Standard C library
  13 .RI ( libc ", " \-lc )
  14 .SH SYNOPSIS
  15 .nf
  16 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  17 .B #include <unistd.h>
  18 .PP
  19 .BI "int getresuid(uid_t *" ruid ", uid_t *" euid ", uid_t *" suid );
  20 .BI "int getresgid(gid_t *" rgid ", gid_t *" egid ", gid_t *" sgid );
  21 .fi
  22 .SH DESCRIPTION
  23 .BR getresuid ()
  24 returns the real UID, the effective UID, and the saved set-user-ID
  25 of the calling process, in the arguments
  26 .IR ruid ,
  27 .IR euid ,
  28 and
  29 .IR suid ,
  30 respectively.
  31 .BR getresgid ()
  32 performs the analogous task for the process's group IDs.
  33 .SH RETURN VALUE
  34 On success, zero is returned.
  35 On error, \-1 is returned, and
  36 .I errno
  37 is set to indicate the error.
  38 .SH ERRORS
  39 .TP
  40 .B EFAULT
  41 One of the arguments specified an address outside the calling program's
  42 address space.
  43 .SH VERSIONS
  44 These system calls appeared on Linux starting with kernel 2.1.44.
  45 .PP
  46 The prototypes are given by glibc since version 2.3.2,
  47 provided
  48 .B _GNU_SOURCE
  49 is defined.
  50 .SH STANDARDS
  51 These calls are nonstandard;
  52 they also appear on HP-UX and some of the BSDs.
  53 .SH NOTES
  54 The original Linux
  55 .BR getresuid ()
  56 and
  57 .BR getresgid ()
  58 system calls supported only 16-bit user and group IDs.
  59 Subsequently, Linux 2.4 added
  60 .BR getresuid32 ()
  61 and
  62 .BR getresgid32 (),
  63 supporting 32-bit IDs.
  64 The glibc
  65 .BR getresuid ()
  66 and
  67 .BR getresgid ()
  68 wrapper functions transparently deal with the variations across kernel versions.
  69 .SH SEE ALSO
  70 .BR getuid (2),
  71 .BR setresuid (2),
  72 .BR setreuid (2),
  73 .BR setuid (2),
  74 .BR credentials (7)