The setpgid() function sets the process group ID of the process with ID pid to pgid.

If pgid is equal to pid, the process becomes a process group leader. See intro(2) for more information on session leaders and process group leaders.

If pgid is not equal to pid, the process becomes a member of an existing process group.

If pid is equal to 0, the process ID of the calling process is used. If pgid is equal to 0, the process specified by pid becomes a process group leader.

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The setpgid() function will fail if:

EACCES

The pid argument matches the process ID of a child process of the calling process and the child process has successfully executed one of the exec family of functions (see exec(2)).

EINVAL

The pgid argument is less than (pid_t) 0 or greater than or equal to PID_MAX, or the calling process has a controlling terminal that does not support job control.

EPERM

The process indicated by the pid argument is a session leader.

EPERM

The pid argument matches the process ID of a child process of the calling process and the child process is not in the same session as the calling process.

EPERM

The pgid argument does not match the process ID of the process indicated by the pid argument, and there is no process with a process group ID that matches pgid in the same session as the calling process.

ESRCH

The pid argument does not match the process ID of the calling process or of a child process of the calling process.

See attributes(5) for descriptions of the following attributes:

intro(2), exec(2), exit(2), fork(2), getpid(2), getsid(2), attributes(5)