setpgid, getpgid, setpgrp, getpgrp - set/get process group
int setpgid(pid_t pid, pid_t pgid));
pid_t getpgid(pid_t pid));
setpgid sets the process group ID of the process specified
by pid to pgid. If pid is zero, the process ID of the
current process is used. If pgid is zero, the process ID of
the process specified by pid is used.
getpgid returns the process group ID of the process speci-
fied by pid. If pid is zero, the process ID of the current
process is used.
In the Linux DLL 4.4.1 library, setpgrp simply calls
getpgrp is equivalent to getpgid(0).
Process groups are used for distribution of signals, and by
terminals to arbitrate requests for their input: processes
that have the same process group as the terminal are fore-
ground and may read, while others will block with a signal
if they attempt to read.
These calls are thus used by programs such as csh(1) to
create process groups in implementing job control. The
TIOCGPGRP and TIOCSPGRP calls described in termios(4) are
used to get/set the process group of the control terminal.
On success, setpgid and setpgrp return zero. On error, -1
is returned, and errno is set appropriately.
getpgid returns a process group on success. On error, -1 is
returned, and errno is set appropriately.
getpgrp always returns the current process group.
EINVAL pgid is less than 0.
EPERM Various permission violations.
ESRCH pid does not match any process.
SVr4, POSIX, 4.4BSD.
The functions setpgid and getpgrp conform to POSIX.1. The
function setpgrp is from BSD 4.2. The function getpgid con-
forms to SVr4.
getuid(2), setsid(2), tcsetpgrp(3), termios(4)