1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)getpgrp.2 8.1 (Berkeley) 6/4/93 29.\" 30.Dd June 4, 1993 31.Dt GETPGRP 2 32.Os 33.Sh NAME 34.Nm getpgrp 35.Nd get process group 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In unistd.h 40.Ft pid_t 41.Fn getpgrp void 42.Ft pid_t 43.Fn getpgid "pid_t pid" 44.Sh DESCRIPTION 45The process group of the current process is returned by 46.Fn getpgrp . 47The process group of the process identified by 48.Fa pid 49is returned by 50.Fn getpgid . 51If 52.Fa pid 53is zero, 54.Fn getpgid 55returns the process group of the current process. 56.Pp 57Process groups are used for distribution of signals, and 58by terminals to arbitrate requests for their input: processes 59that have the same process group as the terminal are foreground 60and may read, while others will block with a signal if they attempt 61to read. 62.Pp 63This system call is thus used by programs such as 64.Xr csh 1 65to create 66process groups 67in implementing job control. 68The 69.Fn tcgetpgrp 70and 71.Fn tcsetpgrp 72calls 73are used to get/set the process group of the control terminal. 74.Sh RETURN VALUES 75The 76.Fn getpgrp 77system call always succeeds. 78Upon successful completion, the 79.Fn getpgid 80system call returns the process group of the specified process; 81otherwise, it returns a value of \-1 and sets 82.Va errno 83to indicate the error. 84.Sh COMPATIBILITY 85This version of 86.Fn getpgrp 87differs from past Berkeley versions by not taking a 88.Fa "pid_t pid" 89argument. 90This incompatibility is required by 91.St -p1003.1-90 . 92.Pp 93From the 94.St -p1003.1-90 95Rationale: 96.Pp 97.Bx 4.3 98provides a 99.Fn getpgrp 100system call that returns the process group ID for a specified process. 101Although this function is used to support job control, all known 102job-control shells always specify the calling process with this 103function. 104Thus, the simpler 105.At V 106.Fn getpgrp 107suffices, and the added complexity of the 108.Bx 4.3 109.Fn getpgrp 110has been omitted from POSIX.1. 111The old functionality is available from the 112.Fn getpgid 113system call. 114.Sh ERRORS 115The 116.Fn getpgid 117system call 118will succeed unless: 119.Bl -tag -width Er 120.It Bq Er ESRCH 121there is no process whose process ID equals 122.Fa pid 123.El 124.Sh SEE ALSO 125.Xr getsid 2 , 126.Xr setpgid 2 , 127.Xr termios 4 128.Sh STANDARDS 129The 130.Fn getpgrp 131system call is expected to conform to 132.St -p1003.1-90 . 133.Sh HISTORY 134The 135.Fn getpgrp 136system call appeared in 137.Bx 4.0 . 138The 139.Fn getpgid 140system call is derived from its usage in 141.At V.4 . 142