setegid()

Set the effective group ID for a process

Synopsis:

#include <unistd.h>

int setegid( gid_t gid );

Arguments:

gid

The effective 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 setegid() function lets the calling process set the effective group ID based on the following:

• If the process is the superuser, the setegid() function sets the effective group ID to gid.
• If the process isn't the superuser, but gid is equal to the real group ID or saved set-group ID, setegid() sets the effective group ID to gid.

The real and saved group ID aren't changed.

---

If a set-group ID process sets its effective group ID to its real group ID, it can still set its effective group ID back to the saved set-group ID.

---

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

Returns:

Zero for success, or -1 if an error occurs (errno is set).

Errors:

EINVAL

The value of gid is out of range.

EPERM

The process isn't the superuser, and gid doesn't match the real group ID or the saved set-group ID.

Examples:

/*
 * This process sets its effective group ID to 2
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int main( void )
{
    gid_t oegid;

    oegid = getegid();
    if( setegid( 2 ) == -1 ) {
        perror( "setegid" );
        return EXIT_FAILURE;
    }

    printf( "Was effective group %d, is 2\n", oegid );
    return EXIT_SUCCESS;
}

Classification:

POSIX 1003.1

See also:

errno, getegid(), seteuid(), setgid(), setuid()