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| <h4 class="subsection">24.2.8 Signal Messages</h4> |
| |
| <p><a name="index-signal-messages-2899"></a> |
| We mentioned above that the shell prints a message describing the signal |
| that terminated a child process. The clean way to print a message |
| describing a signal is to use the functions <code>strsignal</code> and |
| <code>psignal</code>. These functions use a signal number to specify which |
| kind of signal to describe. The signal number may come from the |
| termination status of a child process (see <a href="Process-Completion.html#Process-Completion">Process Completion</a>) or it |
| may come from a signal handler in the same process. |
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| <!-- string.h --> |
| <!-- GNU --> |
| <div class="defun"> |
| — Function: char * <b>strsignal</b> (<var>int signum</var>)<var><a name="index-strsignal-2900"></a></var><br> |
| <blockquote><p>This function returns a pointer to a statically-allocated string |
| containing a message describing the signal <var>signum</var>. You |
| should not modify the contents of this string; and, since it can be |
| rewritten on subsequent calls, you should save a copy of it if you need |
| to reference it later. |
| |
| <p><a name="index-string_002eh-2901"></a>This function is a GNU extension, declared in the header file |
| <samp><span class="file">string.h</span></samp>. |
| </p></blockquote></div> |
| |
| <!-- signal.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: void <b>psignal</b> (<var>int signum, const char *message</var>)<var><a name="index-psignal-2902"></a></var><br> |
| <blockquote><p>This function prints a message describing the signal <var>signum</var> to the |
| standard error output stream <code>stderr</code>; see <a href="Standard-Streams.html#Standard-Streams">Standard Streams</a>. |
| |
| <p>If you call <code>psignal</code> with a <var>message</var> that is either a null |
| pointer or an empty string, <code>psignal</code> just prints the message |
| corresponding to <var>signum</var>, adding a trailing newline. |
| |
| <p>If you supply a non-null <var>message</var> argument, then <code>psignal</code> |
| prefixes its output with this string. It adds a colon and a space |
| character to separate the <var>message</var> from the string corresponding |
| to <var>signum</var>. |
| |
| <p><a name="index-stdio_002eh-2903"></a>This function is a BSD feature, declared in the header file <samp><span class="file">signal.h</span></samp>. |
| </p></blockquote></div> |
| |
| <p><a name="index-sys_005fsiglist-2904"></a>There is also an array <code>sys_siglist</code> which contains the messages |
| for the various signal codes. This array exists on BSD systems, unlike |
| <code>strsignal</code>. |
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