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@(#)getpgrp.2 8.1 (Berkeley) 6/4/93
$FreeBSD: head/lib/libc/sys/getpgrp.2 84306 2001-10-01 16:09:29Z ru $
.Dd June 4, 1993 .Dt GETPGRP 2 .Os .Sh NAME .Nm getpgrp .Nd get process group .Sh LIBRARY .Lb libc .Sh SYNOPSIS n unistd.h .Ft pid_t .Fn getpgrp void .Ft pid_t .Fn getpgid "pid_t pid" .Sh 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.
p 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.
p This call is thus used by programs such as .Xr 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. .Sh RETURN VALUES The .Fn getpgrp call always succeeds. Upon successful completion, the .Fn getpgid call returns the process group of the specified process; otherwise, it returns a value of -1 and sets .Va errno to indicate the error. .Sh ERRORS .Fn getpgid will succeed unless: l -tag -width Er t Bq Er ESRCH there is no process whose process ID equals .Fa pid .El .Sh SEE ALSO .Xr getsid 2 , .Xr setpgid 2 , .Xr termios 4 .Sh HISTORY The .Fn getpgrp function call appeared in x 4.0 . The .Fn getpgid function call is derived from its usage in System V Release 4. .Sh STANDARDS The .Fn getpgrp function call is expected to conform to .St -p1003.1-90 . .Sh 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 .
p From the .St -p1003.1-90 Rationale:
p x 4.3 provides a .Fn getpgrp function 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 V .Fn getpgrp suffices, and the added complexity of the x 4.3 .Fn getpgrp has been omitted from POSIX.1. The old functionality is available from the .Fn getpgid function.