BSD 4_3_Net_2 release

[unix-history] / usr / src / lib / libc / sys / pipe.2

diff --git a/usr/src/lib/libc/sys/pipe.2 b/usr/src/lib/libc/sys/pipe.2
index aa13099..a34cd34 100644 (file)
--- a/usr/src/lib/libc/sys/pipe.2
+++ b/usr/src/lib/libc/sys/pipe.2
@@ -1,80 +1,115 @@
-.\" Copyright (c) 1980 Regents of the University of California.
-.\" All rights reserved.  The Berkeley software License Agreement
-.\" specifies the terms and conditions for redistribution.
+.\" Copyright (c) 1980, 1991 Regents of the University of California.
+.\" All rights reserved.

 .\"
 .\"

-.\"    @(#)pipe.2      6.2 (Berkeley) 8/26/85
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"    This product includes software developed by the University of
+.\"    California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.

 .\"
 .\"

-.TH PIPE 2 "August 26, 1985"
-.UC 4
-.SH NAME
-pipe \- create an interprocess communication channel
-.SH SYNOPSIS
-.nf
-.ft B
-pipe(fildes)
-int fildes[2];
-.fi
-.ft R
-.SH DESCRIPTION
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)pipe.2     6.3 (Berkeley) 3/10/91
+.\"
+.Dd March 10, 1991
+.Dt PIPE 2
+.Os BSD 4
+.Sh NAME
+.Nm pipe
+.Nd create descriptor pair for interprocess communication
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft int
+.Fn pipe "int *fildes"
+.Sh DESCRIPTION

 The
 The

-.I pipe
-system call
-creates an I/O mechanism called a pipe.
-The file descriptors returned can
-be used in read and write operations.
-When the pipe is written using the descriptor
-.IR fildes [1]
-up to 4096 bytes of data are buffered
-before the writing process is suspended.
-A read using the descriptor
-.IR fildes [0]
-will pick up the data.
-.PP
-It is assumed that after the
-pipe has been set up,
-two (or more)
-cooperating processes
-(created by subsequent
-.I fork
-calls)
-will pass data through the
-pipe with
-.I read
-and
-.I write
-calls.
-.PP
-The shell has a syntax
-to set up a linear array of processes
-connected by pipes.
-.PP
-Read calls on an empty
-pipe (no buffered data) with only one end
-(all write file descriptors closed)
-returns an end-of-file.
-.PP
+.Fn pipe
+function
+creates a
+.Em pipe ,
+which is an object allowing
+unidirectional data flow,
+and allocates a pair of file descriptors.
+The first descriptor connects to the
+.Em read end
+of the pipe,
+and the second connects to the
+.Em write end  ,
+so that data written to
+.Fa fildes[1]
+appears on (i.e., can be read from)
+.Fa fildes[0] .
+This allows the output of one program to be
+sent
+to another program:
+the source's standard output is set up to be
+the write end of the pipe,
+and the sink's standard input is set up to be
+the read end of the pipe.
+The pipe itself persists until all its associated descriptors are
+closed.
+.Pp
+A pipe whose read or write end has been closed is considered
+.Em widowed .
+Writing on such a pipe causes the writing process to receive
+a
+.Dv SIGPIPE
+signal.
+Widowing a pipe is the only way to deliver end-of-file to a reader:
+after the reader consumes any buffered data, reading a widowed pipe
+returns a zero count.
+.Pp

 Pipes are really a special case of the 
 Pipes are really a special case of the 

-.IR socketpair (2)
+.Xr socketpair 2

 call and, in fact, are implemented as such in the system.
 call and, in fact, are implemented as such in the system.

-.PP
-A signal is generated if a write on a pipe with only one end is attempted.
-.SH "RETURN VALUE
-The function value zero is returned if the
-pipe was created; \-1 if an error occurred.
-.SH ERRORS
-The \fIpipe\fP call will fail if:
-.TP 15
-[EMFILE]
+.Sh RETURN VALUES
+On successful creation of the pipe, zero is returned. Otherwise, 
+a value of -1 is returned and the variable
+.Va errno
+set to indicate the
+error.
+.Sh ERRORS
+The
+.Fn pipe
+call will fail if:
+.Bl -tag -width [EMFILE]
+.It Bq Er EMFILE

 Too many descriptors are active.
 Too many descriptors are active.

-.TP 15
-[ENFILE]
+.It Bq Er ENFILE

 The system file table is full.
 The system file table is full.

-.TP 15
-[EFAULT]
-The \fIfildes\fP buffer is in an invalid area of the process's address
+.It Bq Er EFAULT
+The
+.Fa fildes
+buffer is in an invalid area of the process's address

 space.
 space.

-.SH "SEE ALSO"
-sh(1), read(2), write(2), fork(2), socketpair(2)
-.SH BUGS
-Should more than 4096 bytes be necessary in any
-pipe among a loop of processes, deadlock will occur.
+.El
+.Sh SEE ALSO
+.Xr sh 1 ,
+.Xr read 2 ,
+.Xr write 2 ,
+.Xr fork 2 ,
+.Xr socketpair 2
+.Sh HISTORY
+A
+.Nm
+function call appeared in Version 6 AT&T UNIX.