getpgid (2)

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(The comments found at the beginning of the groff file "man2/getpgid.2freebsd".)

NAME

getpgrp - get process group

LIBRARY

Lb libc

SYNOPSIS

In unistd.h Ft pid_t Fn getpgrp void Ft pid_t Fn getpgid pid_t pid

DESCRIPTION

The process group of the current process is returned by Fn getpgrp . The process group of the process identified by Fa pid is returned by Fn getpgid . If Fa pid is zero, Fn getpgid returns the process group of the current process.

Process groups are used for distribution of signals, and by terminals to arbitrate requests for their input: processes that have the same process group as the terminal are foreground and may read, while others will block with a signal if they attempt to read.

This system call is thus used by programs such as csh(1) to create process groups in implementing job control. The Fn tcgetpgrp and Fn tcsetpgrp calls are used to get/set the process group of the control terminal.

RETURN VALUES

The Fn getpgrp system call always succeeds. Upon successful completion, the Fn getpgid system call returns the process group of the specified process; otherwise, it returns a value of -1 and sets errno to indicate the error.

COMPATIBILITY

This version of Fn getpgrp differs from past Berkeley versions by not taking a Fa pid_t pid argument. This incompatibility is required by St -p1003.1-90 .

From the St -p1003.1-90 Rationale:

BSD 4.3 provides a Fn getpgrp system call that returns the process group ID for a specified process. Although this function is used to support job control, all known job-control shells always specify the calling process with this function. Thus, the simpler AT&T System V Fn getpgrp suffices, and the added complexity of the BSD 4.3 Fn getpgrp has been omitted from POSIX.1. The old functionality is available from the Fn getpgid system call.

ERRORS

The Fn getpgid system call will succeed unless:

Bq Er ESRCH

there is no process whose process ID equals Fa pid

SEE ALSO

getsid(2), setpgid(2), termios(4)

STANDARDS

The Fn getpgrp system call is expected to conform to St -p1003.1-90 .

HISTORY

The Fn getpgrp system call appeared in BSD 4.0 The Fn getpgid system call is derived from its usage in AT&T System V.4 .