killpg

Killpg is a Unix and Unix-like system interface function that sends a specified signal to all processes in a given process group. It is used to manage or terminate multi-process jobs that share a common process group, such as a pipeline or a script spawning several child processes.

The function typically has the signature int killpg(pid_t pgrp, int sig); and is declared in the system’s signal handling headers. When called, it transmits the signal sig to every process whose process group ID equals pgrp. On success it returns 0; on error it returns -1 and sets errno to indicate the problem, such as ESRCH for a non-existent group or EPERM for insufficient permissions.

Portability and availability vary by platform. Not all systems provide killpg as a separate entry in the C library. On systems without killpg, equivalent behavior can often be achieved by signaling the negative of a process group ID with the standard kill function (for example, kill(-pgrp, sig) on Linux), or by using higher-level utilities such as pkill with the -g option to target a group. Scripts and programs should consider these portability differences when relying on process-group signaling.

Typical use cases include terminating all processes in a job started by a script, sending a gentle shutdown signal to a group of related processes, or implementing job-control behavior in a custom launcher. Developers should exercise caution to avoid signaling critical system or daemon processes, and ensure appropriate permissions are in place when targeting a process group. See also: kill, signals, pkill, process groups.