setgid()

Set the real, effective and saved group IDs

Synopsis:

#include <unistd.h>

int setgid( gid_t gid );

Arguments:

gid

The group ID that you want to use for the process.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

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

• If the process is the superuser, the setgid() function sets the real group ID, effective group ID and saved group ID to gid.
• If the process isn't the superuser, 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.

This function doesn't change any supplementary group IDs of the calling process.

If you wish to change only the effective group ID, and even if you are the superuser, you should consider using the setegid() function.

The "superuser" is defined as any process with an effective user ID of 0, or an effective user ID of root.

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>

int main( void )
  {
    gid_t ogid;

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

Classification:

POSIX 1003.1

See also:

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