killpg - send signal to a process group
pgrp is 0, killpg() sends the signal to
the calling process's process group. (POSIX says: if
less than or equal to 1, the behavior is undefined.)
For the permissions required to send a signal to another process, see kill(2).
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
The process group was given as 0 but the sending process does not have a process group.
There are various differences between the permission checking in BSD-type systems and System V-type systems. See the POSIX rationale for kill(3p). 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.
On Linux, killpg() is implemented as a library
function that makes the call
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