Provided by: manpages-posix-dev_2.16-1_all 
NAME
getpgid - get the process group ID for a process
SYNOPSIS
#include <unistd.h> pid_t getpgid(pid_t pid);
DESCRIPTION
The getpgid() function shall return the process group ID of the process whose process ID is equal to pid.
If pid is equal to 0, getpgid() shall return the process group ID of the calling process.
RETURN VALUE
Upon successful completion, getpgid() shall return a process group ID. Otherwise, it shall return
(pid_t)-1 and set errno to indicate the error.
ERRORS
The getpgid() function shall fail if:
EPERM The process whose process ID is equal to pid is not in the same session as the calling process,
and the implementation does not allow access to the process group ID of that process from the
calling process.
ESRCH There is no process with a process ID equal to pid.
The getpgid() function may fail if:
EINVAL The value of the pid argument is invalid.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
exec() , fork() , getpgrp() , getpid() , getsid() , setpgid() , setsid() , the Base Definitions volume of
IEEE Std 1003.1-2001, <unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .