Mac Developer Library Developer


This manual page is part of Xcode Tools version 5.0

To obtain these tools:

If you are running a version of Xcode Tools other than 5.0, view the documentation locally:

  • In Xcode

  • In Terminal, using the man(1) command

Reading manual pages

Manual pages are intended as a quick reference for people who already understand a technology.

  • To learn how the manual is organized or to learn about command syntax, read the manual page for manpages(5).

  • For more information about this technology, look for other documentation in the Apple Developer Library.

  • For general information about writing shell scripts, read Shell Scripting Primer.

PIPE(2)                     BSD System Calls Manual                    PIPE(2)

     pipe -- create descriptor pair for interprocess communication

     #include <unistd.h>

     pipe(int fildes[2]);

     The pipe() function creates a pipe (an object that allows unidirectional data flow) and allocates a
     pair of file descriptors.  The first descriptor connects to the read end of the pipe; the second con-nects connects
     nects to the write end.

     Data written to fildes[1] appears on (i.e., can be read from) fildes[_].  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; the sink's standard input is set up to be the read end of the pipe.  The pipe itself persists
     until all of its associated descriptors are closed.

     A pipe whose read or write end has been closed is considered widowed.  Writing on such a pipe causes
     the writing process to receive a SIGPIPE signal.  Widowing a pipe is the only way to deliver end-of-file end-offile
     file to a reader: after the reader consumes any buffered data, reading a widowed pipe returns a zero

     The generation of the SIGPIPE signal can be suppressed using the F_SETNOSIGPIPE fcntl command.

     On successful creation of the pipe, zero is returned. Otherwise, a value of -1 is returned and the
     variable errno set to indicate the error.

     The pipe() call will fail if:

     [EFAULT]           The fildes buffer is in an invalid area of the process's address space.

     [EMFILE]           Too many descriptors are active.

     [ENFILE]           The system file table is full.

     sh(1), fork(2), read(2), socketpair(2), fcntl(2), write(2)

     A pipe() function call appeared in Version 6 AT&T UNIX.

4th Berkeley Distribution      February 17, 2011     4th Berkeley Distribution

Reporting Problems

The way to report a problem with this manual page depends on the type of problem:

Content errors
Report errors in the content of this documentation with the feedback links below.
Bug reports
Report bugs in the functionality of the described tool or API through Bug Reporter.
Formatting problems
Report formatting mistakes in the online version of these pages with the feedback links below.