int setgid(gid_t gid);
If the process has appropriate privileges, setgid() shall set the real group ID, effective group ID, and the saved set-group-ID of the calling process to gid.
If the process does not have appropriate privileges, but gid is equal to the real group ID or the saved set-group-ID, setgid() shall set the effective group ID to gid; the real group ID and saved set-group-ID shall remain unchanged.
The setgid() function shall not affect the supplementary group list in any way.
Any supplementary group IDs of the calling process shall remain unchanged.
Upon successful completion, 0 is returned. Otherwise, -1 shall be returned and errno set to indicate the error.
The setgid() function shall fail if:
- The value of the gid argument is invalid and is not supported by the implementation.
The process does not have appropriate privileges and gid does
not match the real group ID or the saved
The following sections are informative.
Refer to the RATIONALE section in setuid() .
COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .