setgid(2) - Linux man page

Name

setgid - set group identity

Synopsis

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

int setgid(gid_t gid);

Description

setgid() sets the effective group ID of the calling process. If the caller is the superuser, the real GID and saved set-group-ID are also set.

Under Linux, setgid() is implemented like the POSIX version with the _POSIX_SAVED_IDS feature. This allows a set-group-ID program that is not set-user-ID-root to drop all of its group privileges, do some un-privileged work, and then reengage the original effective group ID in a secure manner.

Return Value

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

Errors

EPERM
The calling process is not privileged (does not have the CAP_SETGID capability), and gid does not match the real group ID or saved set-group-ID of the calling process.

Conforming to

SVr4, POSIX.1-2001.

Notes

The original Linux setgid() system call supported only 16-bit group IDs. Subsequently, Linux 2.4 added setgid32() supporting 32-bit IDs. The glibc setgid() wrapper function transparently deals with the variation across kernel versions.

See Also

getgid(2), setegid(2), setregid(2), capabilities(7), credentials(7)

Referenced By

access(2), euidaccess(3), proc(5), setgroups(2), setreuid(2), x11vnc(1)