setgid() — Set the group ID

Standards

Standards / Extensions	C or C++	Dependencies
POSIX.1 XPG4 XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _POSIX1_SOURCE 2
#include <unistd.h>

int setgid(gid_t gid);

General description

Sets one or more of the group IDs (GIDs) for the current process to gid.

If gid is the same as the process's real GID or the saved set-group-ID, setgid() always succeeds and sets the effective GID to gid.

If gid is not the same as the process's real GID, setgid() succeeds only if the process has appropriate privileges. If the process has such privileges, setgid() sets the real GID, the effective GID, and saved set GID to gid.

setgid() does not change any supplementary GIDs of the calling process.

Returned value

If successful, setgid() returns 0.

If unsuccessful, setgid() returns -1 and sets errno to one of the following values:

Error Code: Description
EINVAL: The value of gid is incorrect.
EPERM: The process does not have appropriate privileges to set the GID.

Example

CELEBS06

⁄* CELEBS06

   This example sets your GID.

 *⁄
#define _POSIX_SOURCE 1
#include <unistd.h>
#include <stdio.h>

main() {
  printf("your group id is %d\n", (int) getgid());
  if (setgid(500) != 0)
    perror("setgid() error");
  else
    printf("your group id was changed to %d\n",
           (int) getgid());
}

Output

your group id is 512
your group id was changed to 500