setgid(2)

1SETGID(2)                  Linux Programmer's Manual                 SETGID(2)
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NAME

6       setgid - set group identity
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SYNOPSIS

9       #include <sys/types.h>
10       #include <unistd.h>
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12       int setgid(gid_t gid);
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DESCRIPTION

15       setgid()  sets  the  effective group ID of the calling process.  If the
16       caller is the superuser, the real GID and saved set-group-ID  are  also
17       set.
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19       Under  Linux,  setgid()  is implemented like the POSIX version with the
20       _POSIX_SAVED_IDS feature.  This allows a set-group-ID program  that  is
21       not  set-user-ID-root  to drop all of its group privileges, do some un-
22       privileged work, and then reengage the original effective group ID in a
23       secure manner.
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RETURN VALUE

26       On  success,  zero is returned.  On error, -1 is returned, and errno is
27       set appropriately.
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ERRORS

30       EPERM  The calling  process  is  not  privileged  (does  not  have  the
31              CAP_SETGID capability), and gid does not match the real group ID
32              or saved set-group-ID of the calling process.
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CONFORMING TO

35       SVr4, POSIX.1-2001.
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NOTES

38       The original Linux setgid() system call  supported  only  16-bit  group
39       IDs.   Subsequently,  Linux 2.4 added setgid32() supporting 32-bit IDs.
40       The glibc setgid() wrapper function transparently deals with the varia‐
41       tion across kernel versions.
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COLOPHON

47       This  page  is  part of release 3.53 of the Linux man-pages project.  A
48       description of the project, and information about reporting  bugs,  can
49       be found at http://www.kernel.org/doc/man-pages/.
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53Linux                             2010-11-22                         SETGID(2)