fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
143 lines
3.9 KiB
Groff
143 lines
3.9 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getpgrp.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd June 4, 1993
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.Dt GETPGRP 2
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.Os
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.Sh NAME
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.Nm getpgrp
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.Nd get process group
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft pid_t
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.Fn getpgrp void
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.Ft pid_t
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.Fn getpgid "pid_t pid"
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.Sh DESCRIPTION
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The process group of the current process is returned by
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.Fn getpgrp .
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The process group of the process identified by
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.Fa pid
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is returned by
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.Fn getpgid .
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If
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.Fa pid
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is zero,
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.Fn getpgid
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returns the process group of the current process.
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.Pp
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Process groups are used for distribution of signals, and
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by terminals to arbitrate requests for their input: processes
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that have the same process group as the terminal are foreground
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and may read, while others will block with a signal if they attempt
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to read.
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.Pp
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This system call is thus used by programs such as
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.Xr csh 1
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to create
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process groups
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in implementing job control.
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The
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.Fn tcgetpgrp
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and
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.Fn tcsetpgrp
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calls
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are used to get/set the process group of the control terminal.
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.Sh RETURN VALUES
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The
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.Fn getpgrp
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system call always succeeds.
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Upon successful completion, the
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.Fn getpgid
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system call returns the process group of the specified process;
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otherwise, it returns a value of \-1 and sets
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.Va errno
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to indicate the error.
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.Sh COMPATIBILITY
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This version of
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.Fn getpgrp
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differs from past Berkeley versions by not taking a
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.Fa "pid_t pid"
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argument.
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This incompatibility is required by
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.St -p1003.1-90 .
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.Pp
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From the
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.St -p1003.1-90
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Rationale:
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.Pp
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.Bx 4.3
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provides a
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.Fn getpgrp
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system call that returns the process group ID for a specified process.
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Although this function is used to support job control, all known
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job-control shells always specify the calling process with this
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function.
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Thus, the simpler
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.At V
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.Fn getpgrp
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suffices, and the added complexity of the
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.Bx 4.3
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.Fn getpgrp
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has been omitted from POSIX.1.
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The old functionality is available from the
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.Fn getpgid
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system call.
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.Sh ERRORS
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The
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.Fn getpgid
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system call
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will succeed unless:
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.Bl -tag -width Er
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.It Bq Er ESRCH
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there is no process whose process ID equals
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.Fa pid
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.El
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.Sh SEE ALSO
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.Xr getsid 2 ,
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.Xr setpgid 2 ,
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.Xr termios 4
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.Sh STANDARDS
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The
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.Fn getpgrp
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system call is expected to conform to
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.St -p1003.1-90 .
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.Sh HISTORY
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The
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.Fn getpgrp
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system call appeared in
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.Bx 4.0 .
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The
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.Fn getpgid
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system call is derived from its usage in
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.At V.4 .
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