142 lines
3.8 KiB
Groff
142 lines
3.8 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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.\"
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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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