2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
119 lines
3.6 KiB
Groff
119 lines
3.6 KiB
Groff
.\" $NetBSD: pipe.2,v 1.22 2004/05/13 10:20:58 wiz Exp $
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.\"
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.\" Copyright (c) 1980, 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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.\" @(#)pipe.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd July 17, 1994
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.Dt PIPE 2
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.Os
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.Sh NAME
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.Nm pipe
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.Nd create descriptor pair for interprocess communication
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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 int
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.Fn pipe "int fildes[2]"
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.Sh DESCRIPTION
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The
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.Fn pipe
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function
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creates a
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.Em pipe ,
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which is an object allowing
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unidirectional data flow,
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and allocates a pair of file descriptors.
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The first descriptor connects to the
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.Em read end
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of the pipe,
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and the second connects to the
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.Em write end ,
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so that data written to
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.Fa fildes[1]
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appears on (i.e., can be read from)
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.Fa fildes[0] .
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This allows the output of one program to be
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sent
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to another program:
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the source's standard output is set up to be
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the write end of the pipe,
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and the sink's standard input is set up to be
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the read end of the pipe.
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The pipe itself persists until all its associated descriptors are
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closed.
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.Pp
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A pipe whose read or write end has been closed is considered
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.Em widowed .
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Writing on such a pipe causes the writing process to receive
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a
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.Dv SIGPIPE
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signal.
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Widowing a pipe is the only way to deliver end-of-file to a reader:
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after the reader consumes any buffered data, reading a widowed pipe
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returns a zero count.
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.Sh RETURN VALUES
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On successful creation of the pipe, zero is returned.
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Otherwise, a value of \-1 is returned and the variable
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.Va errno
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set to indicate the
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error.
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.Sh ERRORS
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The
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.Fn pipe
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call will fail if:
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.Bl -tag -width Er
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.It Bq Er EMFILE
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Too many descriptors are active.
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.It Bq Er ENFILE
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The system file table is full.
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.It Bq Er EFAULT
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The
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.Fa fildes
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buffer is in an invalid area of the process's address space.
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The reliable detection of this error cannot be guaranteed; when not
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detected, a signal may be delivered to the process, indicating an
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address violation.
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.El
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.Sh SEE ALSO
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.Xr sh 1 ,
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.Xr fork 2 ,
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.Xr read 2 ,
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.Xr socketpair 2 ,
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.Xr write 2
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.Sh STANDARDS
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The
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.Fn pipe
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function conforms to
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.St -p1003.1-90 .
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.Sh HISTORY
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A
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.Fn pipe
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function call appeared in
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.At v6 .
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