| <html lang="en"> |
| <head> |
| <title>Pipes and FIFOs - The GNU C Library</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="The GNU C Library"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="prev" href="File-System-Interface.html#File-System-Interface" title="File System Interface"> |
| <link rel="next" href="Sockets.html#Sockets" title="Sockets"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU C library. |
| |
| This is Edition 0.12, last updated 2007-10-27, |
| of `The GNU C Library Reference Manual', for version |
| 2.8 (Sourcery G++ Lite 2011.03-41). |
| |
| Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, |
| 2003, 2007, 2008, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software Needs Free Documentation'' |
| and ``GNU Lesser General Public License'', the Front-Cover texts being |
| ``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A |
| copy of the license is included in the section entitled "GNU Free |
| Documentation License". |
| |
| (a) The FSF's Back-Cover Text is: ``You have the freedom to |
| copy and modify this GNU manual. Buying copies from the FSF |
| supports it in developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Pipes-and-FIFOs"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Sockets.html#Sockets">Sockets</a>, |
| Previous: <a rel="previous" accesskey="p" href="File-System-Interface.html#File-System-Interface">File System Interface</a>, |
| Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a> |
| <hr> |
| </div> |
| |
| <!-- %MENU% A simple interprocess communication mechanism --> |
| <h2 class="chapter">15 Pipes and FIFOs</h2> |
| |
| <p><a name="index-pipe-1614"></a>A <dfn>pipe</dfn> is a mechanism for interprocess communication; data written |
| to the pipe by one process can be read by another process. The data is |
| handled in a first-in, first-out (FIFO) order. The pipe has no name; it |
| is created for one use and both ends must be inherited from the single |
| process which created the pipe. |
| |
| <p><a name="index-FIFO-special-file-1615"></a>A <dfn>FIFO special file</dfn> is similar to a pipe, but instead of being an |
| anonymous, temporary connection, a FIFO has a name or names like any |
| other file. Processes open the FIFO by name in order to communicate |
| through it. |
| |
| <p>A pipe or FIFO has to be open at both ends simultaneously. If you read |
| from a pipe or FIFO file that doesn't have any processes writing to it |
| (perhaps because they have all closed the file, or exited), the read |
| returns end-of-file. Writing to a pipe or FIFO that doesn't have a |
| reading process is treated as an error condition; it generates a |
| <code>SIGPIPE</code> signal, and fails with error code <code>EPIPE</code> if the |
| signal is handled or blocked. |
| |
| <p>Neither pipes nor FIFO special files allow file positioning. Both |
| reading and writing operations happen sequentially; reading from the |
| beginning of the file and writing at the end. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Creating-a-Pipe.html#Creating-a-Pipe">Creating a Pipe</a>: Making a pipe with the <code>pipe</code> function. |
| <li><a accesskey="2" href="Pipe-to-a-Subprocess.html#Pipe-to-a-Subprocess">Pipe to a Subprocess</a>: Using a pipe to communicate with a |
| child process. |
| <li><a accesskey="3" href="FIFO-Special-Files.html#FIFO-Special-Files">FIFO Special Files</a>: Making a FIFO special file. |
| <li><a accesskey="4" href="Pipe-Atomicity.html#Pipe-Atomicity">Pipe Atomicity</a>: When pipe (or FIFO) I/O is atomic. |
| </ul> |
| |
| </body></html> |
| |
