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NAME

       setgid - set group identity

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       int setgid(gid_t gid);

DESCRIPTION

       setgid()  sets  the  effective group ID of the calling process.  If the
       caller is the superuser, the real GID and saved set-group-ID  are  also
       set.

       Under  Linux,  setgid()  is implemented like the POSIX version with the
       _POSIX_SAVED_IDS feature.  This allows a set-group-ID program  that  is
       not  set-user-ID-root  to drop all of its group privileges, do some un-
       privileged work, and then reengage the original effective group ID in a
       secure manner.

RETURN VALUE

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

ERRORS

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

CONFORMING TO

       SVr4, POSIX.1-2001.

NOTES

       The original Linux setgid() system call  supported  only  16-bit  group
       IDs.   Subsequently,  Linux 2.4 added setgid32() supporting 32-bit IDs.
       The glibc  setgid()  wrapper  function  transparently  deals  with  the
       variation across kernel versions.

SEE ALSO

       getgid(2), setegid(2), setregid(2), capabilities(7), credentials(7)

COLOPHON

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