| <html lang="en"> |
| <head> |
| <title>Initial Signal Actions - 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="up" href="Signal-Actions.html#Signal-Actions" title="Signal Actions"> |
| <link rel="prev" href="Flags-for-Sigaction.html#Flags-for-Sigaction" title="Flags for Sigaction"> |
| <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="Initial-Signal-Actions"></a> |
| <p> |
| Previous: <a rel="previous" accesskey="p" href="Flags-for-Sigaction.html#Flags-for-Sigaction">Flags for Sigaction</a>, |
| Up: <a rel="up" accesskey="u" href="Signal-Actions.html#Signal-Actions">Signal Actions</a> |
| <hr> |
| </div> |
| |
| <h4 class="subsection">24.3.6 Initial Signal Actions</h4> |
| |
| <p><a name="index-initial-signal-actions-2929"></a> |
| When a new process is created (see <a href="Creating-a-Process.html#Creating-a-Process">Creating a Process</a>), it inherits |
| handling of signals from its parent process. However, when you load a |
| new process image using the <code>exec</code> function (see <a href="Executing-a-File.html#Executing-a-File">Executing a File</a>), any signals that you've defined your own handlers for revert to |
| their <code>SIG_DFL</code> handling. (If you think about it a little, this |
| makes sense; the handler functions from the old program are specific to |
| that program, and aren't even present in the address space of the new |
| program image.) Of course, the new program can establish its own |
| handlers. |
| |
| <p>When a program is run by a shell, the shell normally sets the initial |
| actions for the child process to <code>SIG_DFL</code> or <code>SIG_IGN</code>, as |
| appropriate. It's a good idea to check to make sure that the shell has |
| not set up an initial action of <code>SIG_IGN</code> before you establish your |
| own signal handlers. |
| |
| <p>Here is an example of how to establish a handler for <code>SIGHUP</code>, but |
| not if <code>SIGHUP</code> is currently ignored: |
| |
| <pre class="smallexample"> ... |
| struct sigaction temp; |
| |
| sigaction (SIGHUP, NULL, &temp); |
| |
| if (temp.sa_handler != SIG_IGN) |
| { |
| temp.sa_handler = handle_sighup; |
| sigemptyset (&temp.sa_mask); |
| sigaction (SIGHUP, &temp, NULL); |
| } |
| </pre> |
| </body></html> |
| |
