killpgpgrp

killpgpgrp refers to a mechanism or naming convention used for signaling all processes within a specific process group identified by its process group ID (PGID). In Unix-like systems, signals can be sent to individual processes or to groups of processes. The standard POSIX interface uses a process ID (pid) parameter, where a negative pid designates a process group: a negative value of -PGID sends the signal to every process in the group with that PGID.

In practice, there are two common ways to achieve the effect associated with killpgpgrp. In C programming, the function killpg may be used, for example killpg(pgid, sig), which sends the signal sig to all processes in the process group whose ID is PGID. In the shell, the same idea is typically achieved with the kill command by supplying a negative PGID as the target: kill -SIGTERM -1234 sends SIGTERM to all processes in the process group 1234. This behavior relies on the system honoring negative PIDs as group targets.

Notes on behavior and limitations: signals follow general rules for process signaling. If a process is permitted to signal a target, it will receive the signal unless the signal is blocked or ignored by that process. Certain signals, such as SIGKILL and SIGSTOP, cannot be caught or ignored. The exact availability of a dedicated killpgpgrp utility varies by operating system and distribution; some systems provide explicit wrappers like killpg or a library function, while others rely on the standard kill command with a negative PID.

See also: kill, process groups, POSIX signals, killpg (library function).