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Manual page for GETPGRP(2V)

getpgrp, setpgrp - return or set the process group of a process

SYNOPSIS

int getpgrp(pid)
int pid;

int setpgrp(pid, pgrp)
int pgrp;
int pid;

SYSTEM V SYNOPSIS

int getpgrp()

int setpgrp()

DESCRIPTION

getpgrp() returns the process group of the process indicated by pid. If pid is zero, then the call applies to the calling process.

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 run in the foreground and may read from the terminal, while others block with a signal when they attempt to read.

This call is thus used by programs such as csh.1 to create process groups in implementing job control. The TIOCGPGRP and TIOCSPGRP calls described in termio.4 are used to get/set the process group of the control terminal.

setpgrp() sets the process group of the specified process, (pid) to the process group specified by pgrp. If pid is zero, then the call applies to the current (calling) process. If pgrp is zero and pid refers to the calling process, setpgrp() behaves identically to setsid.2v

If the effective user ID of the calling process is not super-user, then the process to be affected must have the same effective user ID as that of the calling process or be a member of the same session as the calling process.

SYSTEM V DESCRIPTION

getpgrp() returns the process group of the calling process.

setpgrp() behaves identically to setsid().

RETURN VALUES

getpgrp() returns the process group of the indicated process on success. On failure, it returns -1 and sets errno to indicate the error.

setpgrp() returns:

0: on success.
-1: on failure and sets errno to indicate the error.

SYSTEM V RETURN VALUES

getpgrp() returns the process group of the calling process on success.

ERRORS

setpgrp() fails, and the process group is not altered when one of the following occurs:

EACCES: The value of pid 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 pgrp is less than zero or is greater than MAXPID, the maximum process ID as defined in <sys/param.h>.
EPERM: The process indicated by pid is a session leader.
: The value of pid is valid but 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.
: The value of pgrp does not match the process ID of the process indicated by pid and there is no process with a process group ID that matches the value of pgrp in the same session as the calling process.
: The requested process has a different effective user ID from that of the calling process and is not a descendent of the calling process.
: The calling process is already a process group leader
: The process ID of the calling process equals the process group ID of a different process.
ESRCH: The value of pid does not match the process ID of the calling process or of a child process of the calling process.
: The requested process does not exist.