setgid()

set the real, effective and saved group IDs

Synopsis:

#include <unistd.h>
int setgid( gid_t gid );

Description:

The setgid() function allows the calling process to set the real, effective and saved group IDs, based on the following:

• If the process has appropriate privileges, the setgid() function sets the real group ID, effective group ID and saved group ID to gid.
• If the process doesn't have the appropriate privileges, but gid is equal to the real group ID, setgid() sets the effective group ID to gid; the real and saved group IDs aren't changed.

Any supplementary group IDs of the calling process remain unchanged by this function call.

If you wish to change only the effective group ID, even if you have appropriate privileges, you should consider using the setegid() function.

Returns:

0

Success

-1

An error occurred. errno is set to indicate the error.

Errors:

EINVAL

The value of gid is invalid.

EPERM

The process doesn't have appropriate privileges, and gid doesn't match the real group ID.

Examples:

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

void main()
  {
    gid_t ogid;

    ogid = getgid();
    if( setgid( 2 ) == -1 ) {
       perror( "setgid" );
       exit( EXIT_FAILURE );
    }
    printf( "Group ID is now 2, was %d\n", ogid );
    exit( EXIT_SUCCESS );
  }

Classification:

POSIX 1003.1

See also:

errno, setegid(), seteuid(), setuid()