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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>nohup</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="nohup"></a> <a name="tag_04_95"></a><!-- nohup --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_04_95_01"></a>NAME</h4><blockquote>nohup - invoke a utility immune to hangups</blockquote><h4><a name="tag_04_95_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>nohup</tt> <i>utility</i> <b>[</b><i>argument</i><tt>...</tt><b>]</b></code></p></blockquote><h4><a name="tag_04_95_03"></a>DESCRIPTION</h4><blockquote><p>The <i>nohup</i> utility shall invoke the utility named by the <i>utility</i> operand with arguments supplied as the<i>argument</i> operands. At the time the named <i>utility</i> is invoked, the SIGHUP signal shall be set to be ignored.</p><p>If the standard output is a terminal, all output written by the named <i>utility</i> to its standard output shall be appended tothe end of the file <b>nohup.out</b> in the current directory. If <b>nohup.out</b> cannot be created or opened for appending, theoutput shall be appended to the end of the file <b>nohup.out</b> in the directory specified by the <i>HOME</i> environmentvariable. If neither file can be created or opened for appending, <i>utility</i> shall not be invoked. If a file is created, thefile's permission bits shall be set to S_IRUSR | S_IWUSR.</p><p>If the standard error is a terminal, all output written by the named <i>utility</i> to its standard error shall be redirected tothe same file descriptor as the standard output.</p></blockquote><h4><a name="tag_04_95_04"></a>OPTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_95_05"></a>OPERANDS</h4><blockquote><p>The following operands shall be supported:</p><dl compact><dt><i>utility</i></dt><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 <ahref="xcu_chap02.html#tag_02_14"><i>Special Built-In Utilities</i></a> , the results are undefined.</dd><dt><i>argument</i></dt><dd>Any string to be supplied as an argument when invoking the utility named by the <i>utility</i> operand.</dd></dl></blockquote><h4><a name="tag_04_95_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_95_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_95_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>The following environment variables shall affect the execution of <i>nohup</i>:</p><dl compact><dt><i>HOME</i></dt><dd>Determine the pathname of the user's home directory: if the output file <b>nohup.out</b> cannot be created in the currentdirectory, the <i>nohup</i> utility shall use the directory named by <i>HOME</i> to create the file.</dd><dt><i>LANG</i></dt><dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> forthe precedence of internationalization variables used to determine the values of locale categories.)</dd><dt><i>LC_ALL</i></dt><dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd><dt><i>LC_CTYPE</i></dt><dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte asopposed to multi-byte characters in arguments).</dd><dt><i>LC_MESSAGES</i></dt><dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standarderror.</dd><dt><i>NLSPATH</i></dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt><i>PATH</i></dt><dd>Determine the search path that is used to locate the utility to be invoked. See the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html">Chapter 8, Environment Variables</a>.</dd></dl></blockquote><h4><a name="tag_04_95_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>The <i>nohup</i> utility shall take the standard action for all signals except that SIGHUP shall be ignored.</p></blockquote><h4><a name="tag_04_95_10"></a>STDOUT</h4><blockquote><p>If the standard output is not a terminal, the standard output of <i>nohup</i> shall be the standard output generated by theexecution of the <i>utility</i> specified by the operands. Otherwise, nothing shall be written to the standard output.</p></blockquote><h4><a name="tag_04_95_11"></a>STDERR</h4><blockquote><p>If the standard output is a terminal, a message shall be written to the standard error, indicating the name of the file to whichthe output is being appended. The name of the file shall be either <b>nohup.out</b> or <b>$HOME/nohup.out</b>.</p></blockquote><h4><a name="tag_04_95_12"></a>OUTPUT FILES</h4><blockquote><p>If the standard output is a terminal, all output written by the named <i>utility</i> to the standard output and standard erroris appended to the file <b>nohup.out</b>, which is created if it does not already exist.</p></blockquote><h4><a name="tag_04_95_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_95_14"></a>EXIT STATUS</h4><blockquote><p>The following exit values shall be returned:</p><dl compact><dt>126</dt><dd>The utility specified by <i>utility</i> was found but could not be invoked.</dd><dt>127</dt><dd>An error occurred in the <i>nohup</i> utility or the utility specified by <i>utility</i> could not be found.</dd></dl><p>Otherwise, the exit status of <i>nohup</i> shall be that of the utility specified by the <i>utility</i> operand.</p></blockquote><h4><a name="tag_04_95_15"></a>CONSEQUENCES OF ERRORS</h4><blockquote><p>Default.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_04_95_16"></a>APPLICATION USAGE</h4><blockquote><p>The <a href="../utilities/command.html"><i>command</i></a>, <a href="../utilities/env.html"><i>env</i></a>, <a href="../utilities/nice.html"><i>nice</i></a>, <i>nohup</i>, <a href="../utilities/time.html"><i>time</i></a>, and <a href="../utilities/xargs.html"><i>xargs</i></a> utilities have been specified to use exit code 127 if an error occurs so thatapplications can distinguish "failure to find a utility" from "invoked utility exited with an error indication". The value 127was chosen because it is not commonly used for other meanings; most utilities use small values for "normal error conditions" andthe values above 128 can be confused with termination due to receipt of a signal. The value 126 was chosen in a similar manner toindicate that the utility could be found, but not invoked. Some scripts produce meaningful error messages differentiating the 126and 127 cases. The distinction between exit codes 126 and 127 is based on KornShell practice that uses 127 when all attempts to<i>exec</i> the utility fail with [ENOENT], and uses 126 when any attempt to <i>exec</i> the utility fails for any otherreason.</p></blockquote><h4><a name="tag_04_95_17"></a>EXAMPLES</h4><blockquote><p>It is frequently desirable to apply <i>nohup</i> to pipelines or lists of commands. This can be done by placing pipelines andcommand lists in a single file; this file can then be invoked as a utility, and the <i>nohup</i> applies to everything in thefile.</p><p>Alternatively, the following command can be used to apply <i>nohup</i> to a complex command:</p><pre><tt>nohup sh -c '</tt><i>complex-command-line</i><tt>'</tt></pre></blockquote><h4><a name="tag_04_95_18"></a>RATIONALE</h4><blockquote><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<b>$HOME/nohup.out</b>.</p><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 volumeof IEEE Std 1003.1-2001.</p><p>The term <i>utility</i> is used, rather than <i>command</i>, to highlight the fact that shell compound commands, pipelines,special built-ins, and so on, cannot be used directly. However, <i>utility</i> includes user application programs and shellscripts, not just the standard utilities.</p><p>Historical versions of the <i>nohup</i> utility use default file creation semantics. Some more recent versions use thepermissions specified here as an added security precaution.</p><p>Some historical implementations ignore SIGQUIT in addition to SIGHUP; others ignore SIGTERM. An early proposal allowed, but didnot require, SIGQUIT to be ignored. Several reviewers objected that <i>nohup</i> should only modify the handling of SIGHUP asrequired by this volume of IEEE Std 1003.1-2001.</p></blockquote><h4><a name="tag_04_95_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_95_20"></a>SEE ALSO</h4><blockquote><p><a href="xcu_chap02.html#tag_02"><i>Shell Command Language</i></a> , <a href="sh.html"><i>sh</i></a> , the System Interfacesvolume of IEEE Std 1003.1-2001, <a href="../functions/signal.html"><i>signal</i>()</a></p></blockquote><h4><a name="tag_04_95_21"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 2.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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