273 lines
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273 lines
11 KiB
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<title>nohup</title>
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<basefont size="3"> <a name="nohup"></a> <a name="tag_04_95"></a><!-- nohup -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_04_95_01"></a>NAME</h4>
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<blockquote>nohup - invoke a utility immune to hangups</blockquote>
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<h4><a name="tag_04_95_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>nohup</tt> <i>utility</i> <b>[</b><i>argument</i><tt>...</tt><b>]</b></code></p>
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</blockquote>
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<h4><a name="tag_04_95_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>nohup</i> utility shall invoke the utility named by the <i>utility</i> operand with arguments supplied as the
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<i>argument</i> operands. At the time the named <i>utility</i> is invoked, the SIGHUP signal shall be set to be ignored.</p>
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<p>If the standard output is a terminal, all output written by the named <i>utility</i> to its standard output shall be appended to
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the end of the file <b>nohup.out</b> in the current directory. If <b>nohup.out</b> cannot be created or opened for appending, the
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output shall be appended to the end of the file <b>nohup.out</b> in the directory specified by the <i>HOME</i> environment
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variable. If neither file can be created or opened for appending, <i>utility</i> shall not be invoked. If a file is created, the
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file's permission bits shall be set to S_IRUSR | S_IWUSR.</p>
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<p>If the standard error is a terminal, all output written by the named <i>utility</i> to its standard error shall be redirected to
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the same file descriptor as the standard output.</p>
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</blockquote>
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<h4><a name="tag_04_95_04"></a>OPTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_95_05"></a>OPERANDS</h4>
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<blockquote>
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<p>The following operands shall be supported:</p>
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<dl compact>
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<dt><i>utility</i></dt>
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<dd>The name of a utility that is to be invoked. If the <i>utility</i> operand names any of the special built-in utilities in <a
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href="xcu_chap02.html#tag_02_14"><i>Special Built-In Utilities</i></a> , the results are undefined.</dd>
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<dt><i>argument</i></dt>
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<dd>Any string to be supplied as an argument when invoking the utility named by the <i>utility</i> operand.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_95_06"></a>STDIN</h4>
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<blockquote>
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<p>Not used.</p>
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</blockquote>
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<h4><a name="tag_04_95_07"></a>INPUT FILES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_95_08"></a>ENVIRONMENT VARIABLES</h4>
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<blockquote>
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<p>The following environment variables shall affect the execution of <i>nohup</i>:</p>
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<dl compact>
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<dt><i>HOME</i></dt>
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<dd>Determine the pathname of the user's home directory: if the output file <b>nohup.out</b> cannot be created in the current
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directory, the <i>nohup</i> utility shall use the directory named by <i>HOME</i> to create the file.</dd>
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<dt><i>LANG</i></dt>
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<dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> for
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the precedence of internationalization variables used to determine the values of locale categories.)</dd>
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<dt><i>LC_ALL</i></dt>
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<dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
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<dt><i>LC_CTYPE</i></dt>
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<dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments).</dd>
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<dt><i>LC_MESSAGES</i></dt>
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<dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard
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error.</dd>
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<dt><i>NLSPATH</i></dt>
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<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></dd>
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<dt><i>PATH</i></dt>
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<dd>Determine the search path that is used to locate the utility to be invoked. See the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html">Chapter 8, Environment Variables</a>.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_95_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>The <i>nohup</i> utility shall take the standard action for all signals except that SIGHUP shall be ignored.</p>
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</blockquote>
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<h4><a name="tag_04_95_10"></a>STDOUT</h4>
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<blockquote>
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<p>If the standard output is not a terminal, the standard output of <i>nohup</i> shall be the standard output generated by the
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execution of the <i>utility</i> specified by the operands. Otherwise, nothing shall be written to the standard output.</p>
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</blockquote>
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<h4><a name="tag_04_95_11"></a>STDERR</h4>
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<blockquote>
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<p>If the standard output is a terminal, a message shall be written to the standard error, indicating the name of the file to which
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the output is being appended. The name of the file shall be either <b>nohup.out</b> or <b>$HOME/nohup.out</b>.</p>
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</blockquote>
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<h4><a name="tag_04_95_12"></a>OUTPUT FILES</h4>
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<blockquote>
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<p>If the standard output is a terminal, all output written by the named <i>utility</i> to the standard output and standard error
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is appended to the file <b>nohup.out</b>, which is created if it does not already exist.</p>
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</blockquote>
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<h4><a name="tag_04_95_13"></a>EXTENDED DESCRIPTION</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_95_14"></a>EXIT STATUS</h4>
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<blockquote>
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<p>The following exit values shall be returned:</p>
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<dl compact>
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<dt>126</dt>
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<dd>The utility specified by <i>utility</i> was found but could not be invoked.</dd>
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<dt>127</dt>
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<dd>An error occurred in the <i>nohup</i> utility or the utility specified by <i>utility</i> could not be found.</dd>
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</dl>
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<p>Otherwise, the exit status of <i>nohup</i> shall be that of the utility specified by the <i>utility</i> operand.</p>
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</blockquote>
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<h4><a name="tag_04_95_15"></a>CONSEQUENCES OF ERRORS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_04_95_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <a href="../utilities/command.html"><i>command</i></a>, <a href="../utilities/env.html"><i>env</i></a>, <a href=
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"../utilities/nice.html"><i>nice</i></a>, <i>nohup</i>, <a href="../utilities/time.html"><i>time</i></a>, and <a href=
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"../utilities/xargs.html"><i>xargs</i></a> utilities have been specified to use exit code 127 if an error occurs so that
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applications can distinguish "failure to find a utility" from "invoked utility exited with an error indication". The value 127
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was chosen because it is not commonly used for other meanings; most utilities use small values for "normal error conditions" and
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the values above 128 can be confused with termination due to receipt of a signal. The value 126 was chosen in a similar manner to
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indicate that the utility could be found, but not invoked. Some scripts produce meaningful error messages differentiating the 126
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and 127 cases. The distinction between exit codes 126 and 127 is based on KornShell practice that uses 127 when all attempts to
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<i>exec</i> the utility fail with [ENOENT], and uses 126 when any attempt to <i>exec</i> the utility fails for any other
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reason.</p>
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</blockquote>
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<h4><a name="tag_04_95_17"></a>EXAMPLES</h4>
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<blockquote>
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<p>It is frequently desirable to apply <i>nohup</i> to pipelines or lists of commands. This can be done by placing pipelines and
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command lists in a single file; this file can then be invoked as a utility, and the <i>nohup</i> applies to everything in the
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file.</p>
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<p>Alternatively, the following command can be used to apply <i>nohup</i> to a complex command:</p>
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<pre>
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<tt>nohup sh -c '</tt><i>complex-command-line</i><tt>'
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_04_95_18"></a>RATIONALE</h4>
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<blockquote>
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<p>The 4.3 BSD version ignores SIGTERM and SIGHUP, and if <b>./nohup.out</b> cannot be used, it fails instead of trying to use
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<b>$HOME/nohup.out</b>.</p>
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<p>The <i>csh</i> utility has a built-in version of <i>nohup</i> that acts differently from the <i>nohup</i> defined in this volume
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of IEEE Std 1003.1-2001.</p>
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<p>The term <i>utility</i> is used, rather than <i>command</i>, to highlight the fact that shell compound commands, pipelines,
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special built-ins, and so on, cannot be used directly. However, <i>utility</i> includes user application programs and shell
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scripts, not just the standard utilities.</p>
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<p>Historical versions of the <i>nohup</i> utility use default file creation semantics. Some more recent versions use the
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permissions specified here as an added security precaution.</p>
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<p>Some historical implementations ignore SIGQUIT in addition to SIGHUP; others ignore SIGTERM. An early proposal allowed, but did
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not require, SIGQUIT to be ignored. Several reviewers objected that <i>nohup</i> should only modify the handling of SIGHUP as
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required by this volume of IEEE Std 1003.1-2001.</p>
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</blockquote>
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<h4><a name="tag_04_95_19"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_95_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="xcu_chap02.html#tag_02"><i>Shell Command Language</i></a> , <a href="sh.html"><i>sh</i></a> , the System Interfaces
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volume of IEEE Std 1003.1-2001, <a href="../functions/signal.html"><i>signal</i>()</a></p>
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</blockquote>
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<h4><a name="tag_04_95_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 2.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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<center><font size="2"><!--footer start-->
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