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131 lines
4.1 KiB
Groff
131 lines
4.1 KiB
Groff
.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.TH PIPE 2 "16 January 1997" GNO "System Calls"
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.SH NAME
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.BR pipe
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\- create descriptor pair for interprocess communication
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.SH SYNOPSIS
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.br
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#include <unistd.h>
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.sp 1
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int
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\fBpipe\fR (int *\fIfildes\fR);
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.SH DESCRIPTION
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The
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.BR pipe
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function
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creates a
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.IR 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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.IR read
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end of the pipe,
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and the second connects to the
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.IR write
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end, so that data written to
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.I fildes[1]
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appears on (i.e., can be read from)
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.IR 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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.LP
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A pipe whose read or write end has been closed is considered
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.IR 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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.BR 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 (end of file).
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.SH LIMITS
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Up to 4096 bytes of data are buffered before the writing process is
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suspended. Should more than 4096 bytes be necessary in any pipe among
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a loop of processes, deadlock will occur. This is not a limitation
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specific to GNO but to multiprogramming in general.
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.SH NOTES
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This man page refers to the Unix
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.BR read (2)
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and
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.BR write (2)
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operations. On the IIgs, the described behavior refer to any system
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calls doing I/O, including:
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.RS
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.nf
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GS/OS ReadGS and WriteGS
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TextTools calls
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C stdio I/O routines
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.fi
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.RE
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.SH RETURN VALUES
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On successful creation of the pipe, zero is returned. Otherwise,
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a value of -1 is returned and the variable
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.IR 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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.BR pipe
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call will fail if:
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.RS
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.IP \fBEMFILE\fR
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Too many descriptors are active.
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.IP \fBENFILE\fR
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The system file table is full.
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.IP \fBEFAULT\fR
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The
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.I fildes
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buffer is in an invalid area of the process's address
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space.
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.RE
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.SH SEE ALSO
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.BR sh (1),
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.BR read (2),
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.BR write (2),
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.BR fork (2),
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.BR socketpair (2)
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.SH HISTORY
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A
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.BR pipe
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function call appeared in Version 6 AT&T UNIX.
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