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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>head</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_001_014_928"> </a>NAME</h4><blockquote>head - copy the first part of files</blockquote><h4><a name = "tag_001_014_929"> </a>SYNOPSIS</h4><blockquote><pre><code>head <b>[</b>-n <i>number</i><b>][</b><i>file</i>...<b>]</b>head <b>[</b><i>number</i><b>][</b><i>file</i>...<b>]</b></code></pre></blockquote><h4><a name = "tag_001_014_930"> </a>DESCRIPTION</h4><blockquote>The<i>head</i>utility will copy its input files to the standard output,ending the output for each file at a designated point.<p>Copying will end at the point in each input file indicated by the<b>-n</b> <i>number</i>option(or the<b>-</b><i>number</i>argument).The option-argument<i>number</i>will be counted in units of lines.</blockquote><h4><a name = "tag_001_014_931"> </a>OPTIONS</h4><blockquote>The<i>head</i>utility supports the <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b> </a> ,except that the obsolescent version accepts multi-character numeric options.<p>The following options are supported:<dl compact><dt><b>-n </b><i>number</i><dd>The first<i>number</i>lines of each input file will be copied tostandard output.The<i>number</i>option-argument must be a positive decimal integer.<dt><b>-</b><i>number</i><dd>The<i>number</i>argument is a positive decimal integer with thesame effect as the <b>-n </b><i>number</i> option.</dl><p>If no options are specified,<i>head</i>will act as if<b>-n 10</b>had been specified.</blockquote><h4><a name = "tag_001_014_932"> </a>OPERANDS</h4><blockquote>The following operand is supported:<dl compact><dt><i>file</i><dd>A pathname of an input file.If no<i>file</i>operands are specified,the standard input will be used.</dl></blockquote><h4><a name = "tag_001_014_933"> </a>STDIN</h4><blockquote>The standard input will be used only if no<i>file</i>operands are specified.See the INPUT FILES section.</blockquote><h4><a name = "tag_001_014_934"> </a>INPUT FILES</h4><blockquote>Input files must be text files, but the line lengthis not restricted to{LINE_MAX}bytes.</blockquote><h4><a name = "tag_001_014_935"> </a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables affect the execution of<i>head</i>:<dl compact><dt><i>LANG</i><dd>Provide a default value for the internationalisation variablesthat are unset or null.If<i>LANG</i>is unset or null, the corresponding value from theimplementation-dependent default locale will be used.If any of the internationalisation variables contains an invalid setting, theutility will behave as if none of the variables had been defined.<dt><i>LC_ALL</i><dd>If set to a non-empty string value,override the values of all the other internationalisation variables.<dt><i>LC_CTYPE</i><dd>Determine thelocale for the interpretation of sequences of bytes of text data ascharacters (for example, single- as opposed to multi-byte charactersin arguments and input files).<dt><i>LC_MESSAGES</i><dd>Determine the locale that should be used to affectthe format and contents of diagnosticmessages written to standard error.<dt><i>NLSPATH</i><dd>Determine the location of message cataloguesfor the processing of<i>LC_MESSAGES .</i></dl></blockquote><h4><a name = "tag_001_014_936"> </a>ASYNCHRONOUS EVENTS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_937"> </a>STDOUT</h4><blockquote>The standard output will containdesignated portions of the input files.<p>If multiple<i>file</i>operands are specified,<i>head</i>will precede the output for each with the header:<p><code><tt>"\n==> %s <==\n"</tt>, <<i>pathname</i>></code>except that the first header written will not include the initialnewline character.</blockquote><h4><a name = "tag_001_014_938"> </a>STDERR</h4><blockquote>Used only for diagnostic messages.</blockquote><h4><a name = "tag_001_014_939"> </a>OUTPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_940"> </a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_941"> </a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd>Successful completion.<dt>>0<dd>An error occurred.</dl></blockquote><h4><a name = "tag_001_014_942"> </a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_943"> </a>APPLICATION USAGE</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_944"> </a>EXAMPLES</h4><blockquote>To write the first ten lines of all files(except those with a leading period)in the directory:<pre><code>head *</code></pre></blockquote><h4><a name = "tag_001_014_945"> </a>FUTURE DIRECTIONS</h4><blockquote>The obsolescent<i>-number</i>form may be withdrawn in a future issue.Applications should use the<b>-n</b> <i>number</i>option.</blockquote><h4><a name = "tag_001_014_946"> </a>SEE ALSO</h4><blockquote><i><a href="sed.html">sed</a></i>,<i><a href="tail.html">tail</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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