SETREGID(2)

NAME
setregid - set real and effective group IDs

SYNOPSIS
#include <unistd.h>
int
setregid(gid_t rgid, gid_t egid);

DESCRIPTION
The real and effective group IDs of the current process are set according to the arguments. The saved group ID will be set to the new value of the real group ID if a real group ID is specified and either the new real group ID value is different from the current value or the effective group ID is changed to a value other than the current saved group ID.

Unprivileged users may change either group ID to the current value of the real, effective, or saved group ID. Only the superuser may make other changes.

Supplying a value of -1 for either the real or effective group ID forces the system to substitute the current ID in place of the -1 parameter.

The setregid() function was intended to allow swapping the real and effective group IDs in set-group-ID programs to temporarily relinquish the set-group-ID value. This purpose is now better served by the use of the setegid(2) function.

When setting the real and effective group IDs to the same value, the setgid(2) function is preferred.

RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

[EPERM]
    The current process is not the superuser and a change other than changing the effective group ID to the real group ID was specified.

SEE ALSO
getgid(2), setegid(2), setgid(2), setresgid(2), setreuid(2)

STANDARDS
The setregid() function conforms to the p1003.1-2001 and xpg4.3. specifications.

Note, however, that prior to p1003.1-2001, the setregid() function was not a part of the p1003.1 specification. As a result, it may not be implemented on all systems.

HISTORY
The setregid() function call appeared in 4.2BSD. A semantically different version appeared in 4.4BSD. The current version, with the original semantics restored, appeared in OpenBSD 3.3.

CAVEATS
The setregid() function predates POSIX saved group IDs. This implementation changes the saved group ID to the new value of the real group ID only if the real group ID is specified and either changed or the effective group ID is changed to a value other than the current saved group ID. Other implementations may behave differently.