killpg — send signal to a process group


#include <signal.h>

int killpg(int pgrp, int sig);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


   || /* Since glibc 2.19: */ _DEFAULT_SOURCE
   || /* Glibc versions <= 2.19: */ _BSD_SOURCE


killpg() sends the signal sig to the process group pgrp. See signal(7) for a list of signals.

If pgrp is 0, killpg() sends the signal to the calling process's process group. (POSIX says: if pgrp is less than or equal to 1, the behavior is undefined.)

For the permissions required to send a signal to another process, see kill(2).

Return Value

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.



sig is not a valid signal number.


The process does not have permission to send the signal to any of the target processes. For the required permissions, see kill(2).


No process can be found in the process group specified by pgrp.


The process group was given as 0 but the sending process does not have a process group.

Conforming to

POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (killpg() first appeared in 4BSD).


There are various differences between the permission checking in BSD-type systems and System V-type systems. See the POSIX rationale for kill(). A difference not mentioned by POSIX concerns the return value EPERM: BSD documents that no signal is sent and EPERM returned when the permission check failed for at least one target process, while POSIX documents EPERM only when the permission check failed for all target processes.

C library/kernel differences

On Linux, killpg() is implemented as a library function that makes the call kill(-pgrp, sig).

See Also

getpgrp(2), kill(2), signal(2), capabilities(7), credentials(7)


This page is part of release 5.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

credentials(7), kill(2), sigaction(2), signal(2), signal(7), tcsh(1).

The man page killpg(2) is an alias of killpg(3).

2017-09-15 Linux Programmer's Manual