setpgid()

join or create a process group

Synopsis:

#include <unistd.h>
int setpgid( pid_t pid, pid_t pgid );

The setpgid() function is used either to join an existing process group or to create a new process group within the session of the calling process. The process group ID of a session leader will not change. Upon successful completion, the process group ID of the process with a process ID matching pid is set to pgid. As a special case, either pid or pgid may be specified as zero, meaning that the process ID of the calling process is to be used.

Returns:

0: Success
-1: An error occurred. errno is set to indicate the error.

Errors:

EACCES: The value of 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... functions.
EINVAL: The value of pgid is less than zero.
ENOSYS: The setpgid() function isnt supported by this implementation (included for POSIX compatibility).
EPERM: The calling process doesnt have sufficient privilege to set the process group ID pgid on process pid.
ESRCH: The process pid doesnt exist.

Examples:

/*
 * The process joins process group 0
 */
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>

void main()
  {
    if( setpgid( getpid(), 0 ) == -1 ) {
    perror( "segpgid" );
    }
    printf( "%d belongs to process group %d\n",
         getpid(), getpgrp() );
  }

Classification:

POSIX 1003.1

Safety:
Interrupt handler	No
Signal handler	Yes, but modifies errno
Thread	Yes