SETPGID(2) System Calls Manual SETPGID(2)

setpgid, setpgrp — set process group

Standard C Library (libc, -lc)

#include <unistd.h>

int
setpgid(pid_t pid, pid_t pgrp);

int
setpgrp(pid_t pid, pid_t pgrp);

() sets the process group of the specified process pid to the specified pgrp. If pid is zero, then the call applies to the current process. If pgrp is zero, then the process id of the process specified by pid is used instead.

If the invoker is not the super-user, then the affected process must have the same effective user-id as the invoker or be a descendant of the invoking process.

In general to set the process group of a newly forked subprocess, both the child and parent processes should call () to ensure that the process group change takes effect in a timely fashion. One call will succeed and the other will fail, depending on process scheduling.

setpgid() returns 0 when the operation was successful. If the request failed, -1 is returned and the global variable errno indicates the reason.

setpgrp() is identical to setpgid(), and is retained for calling convention compatibility with historical versions of BSD.

setpgid() will fail and the process group will not be altered if:

[]
The value of the pid argument matches the process ID of a child process of the calling process, and the child process has successfully executed one of the exec functions.
[]
The value of the pgrp argument is less than zero.
[]
The effective user ID of the requested process is different from that of the caller and the process is not a descendant of the calling process.
[]
The value of the pid argument does not match the process ID of the calling process or of a child process of the calling process.

getpgrp(2)

The setpgid() function conforms to IEEE Std 1003.1-1990 (“POSIX.1”).

March 15, 2022 NetBSD 11.0