killpg() — Send a signal to a process group

Standards

Standards / Extensions	C or C++	Dependencies
XPG4.2 Single UNIX Specification, Version 3	both	POSIX(ON)

Format

#define _XOPEN_SOURCE_EXTENDED 1
#include <signal.h>

int killpg(pid_t pgrp, int sig);

General description

The killpg() function sends a signal to a process group.

A process has permission to send a signal if the real or effective user ID of the sender is the same as the real or effective user ID of the intended recipient. A process can also send signals if it has appropriate privileges. If _POSIX_SAVED_IDS is defined in the <unistd.h> include file, the saved set user ID of the intended recipient is checked instead of its effective user ID.

Regardless of user ID, a process can always send a SIGCONT signal to a process group that is a member of the same session (same session ID) as the sender.

pid_t pgrp;

Specifies the process group that the caller wants to send a signal to:

If pgrp is greater than one, killpg() sends the signal, sig, to the process whose process group ID is equal to pgrp and which the sender has appropriate privileges to send a signal.
If pgrp is equal to or less than one, killpg() returns a -1 and sets errno to EINVAL.

int sig;

The signal that should be sent to the processes specified by pid. (For a list of signals, see Table 1.) This must be zero, or one of the signals defined in the <signal.h> include file. If sig is zero, killpg() performs error checking but doesn't really send a signal. You can code sig as zero to check whether the pid argument is valid.

This function is supported only in a POSIX program.

Usage notes

The use of the SIGTHSTOP and SIGTHCONT signal is not supported with this function.

Returned value

If successful, killpg() returns 0 if it has permission to send sig to any of the processes in the process group ID specified by pgrp.

If unsuccessful, killpg() returns -1 and sets errno to one of the following values:

Error Code: Description
EINVAL: The value of sig is incorrect or is not the number of a supported signal, or the value of pgrp is less than or equal to one.
EPERM: The caller does not have permission to send the signal to any process in the process group ID specified by pgrp.
ESRCH: There are no process groups corresponding to pgrp.