<html lang="en">
<head>
<title>Processes - 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="Program-Basics.html#Program-Basics" title="Program Basics">
<link rel="next" href="Job-Control.html#Job-Control" title="Job Control">
<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="Processes"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="Job-Control.html#Job-Control">Job Control</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Program-Basics.html#Program-Basics">Program Basics</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="index.html#Top">Top</a>
<hr>
</div>

<!-- %MENU% How to create processes and run other programs -->
<h2 class="chapter">26 Processes</h2>

<p><a name="index-process-3147"></a><dfn>Processes</dfn> are the primitive units for allocation of system
resources.  Each process has its own address space and (usually) one
thread of control.  A process executes a program; you can have multiple
processes executing the same program, but each process has its own copy
of the program within its own address space and executes it
independently of the other copies.

   <p><a name="index-child-process-3148"></a><a name="index-parent-process-3149"></a>Processes are organized hierarchically.  Each process has a <dfn>parent
process</dfn> which explicitly arranged to create it.  The processes created
by a given parent are called its <dfn>child processes</dfn>.  A child
inherits many of its attributes from the parent process.

   <p>This chapter describes how a program can create, terminate, and control
child processes.  Actually, there are three distinct operations
involved: creating a new child process, causing the new process to
execute a program, and coordinating the completion of the child process
with the original program.

   <p>The <code>system</code> function provides a simple, portable mechanism for
running another program; it does all three steps automatically.  If you
need more control over the details of how this is done, you can use the
primitive functions to do each step individually instead.

<ul class="menu">
<li><a accesskey="1" href="Running-a-Command.html#Running-a-Command">Running a Command</a>:            The easy way to run another program. 
<li><a accesskey="2" href="Process-Creation-Concepts.html#Process-Creation-Concepts">Process Creation Concepts</a>:    An overview of the hard way to do it. 
<li><a accesskey="3" href="Process-Identification.html#Process-Identification">Process Identification</a>:       How to get the process ID of a process. 
<li><a accesskey="4" href="Creating-a-Process.html#Creating-a-Process">Creating a Process</a>:           How to fork a child process. 
<li><a accesskey="5" href="Executing-a-File.html#Executing-a-File">Executing a File</a>:             How to make a process execute another program. 
<li><a accesskey="6" href="Process-Completion.html#Process-Completion">Process Completion</a>:           How to tell when a child process has completed. 
<li><a accesskey="7" href="Process-Completion-Status.html#Process-Completion-Status">Process Completion Status</a>:    How to interpret the status value
                                 returned from a child process. 
<li><a accesskey="8" href="BSD-Wait-Functions.html#BSD-Wait-Functions">BSD Wait Functions</a>:   	More functions, for backward compatibility. 
<li><a accesskey="9" href="Process-Creation-Example.html#Process-Creation-Example">Process Creation Example</a>:     A complete example program. 
</ul>

   </body></html>