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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>umask</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_2448"> </a>NAME</h4><blockquote>umask - get or set the file mode creation mask</blockquote><h4><a name = "tag_001_014_2449"> </a>SYNOPSIS</h4><blockquote><pre><code>umask <b>[</b>-S<b>][</b><i>mask</i><b>]</b></code></pre></blockquote><h4><a name = "tag_001_014_2450"> </a>DESCRIPTION</h4><blockquote>The<i>umask</i>utility will set the file mode creation mask of thecurrent shell execution environment (see<xref href=shexenv><a href="chap2.html#tag_001_012">Shell Execution Environment</a></xref>)to the value specified by the<i>mask</i>operand.This mask will affect the initial value of the file permission bitsof subsequently created files.If<i>umask</i>is called in a subshell or separate utility execution environment,such as one of the following:<pre><code>(umask 002)nohup umask ...find . -exec umask ... \;</code></pre>it will not affect the file mode creation mask of the caller's environment.<p>If the<i>mask</i>operand is not specified, the<i>umask</i>utility will write to standard output the value of the invokingprocess's file mode creation mask.</blockquote><h4><a name = "tag_001_014_2451"> </a>OPTIONS</h4><blockquote>The<i>umask</i>utility supports the <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b> </a> .<p>The following option is supported:<dl compact><dt><b>-S</b><dd>Produce symbolic output.</dl><p>The default output style is unspecified, but will be recognisedon a subsequent invocation of<i>umask</i>on the same system as a<i>mask</i>operand to restore the previous file mode creation mask.</blockquote><h4><a name = "tag_001_014_2452"> </a>OPERANDS</h4><blockquote>The following operand is supported:<dl compact><dt><i>mask</i><dd>A string specifying the new file mode creation mask.The string is treated in the same way as the<i>mode</i>operand described in the the EXTENDED DESCRIPTION sectionfor<i><a href="chmod.html">chmod</a></i>.For a<i>symbolic_mode</i>value,the new value of the file mode creation maskwill be the logical complement of the file permission bitsportion of the file mode specified by the<i>symbolic_mode</i>string.In a<i>symbolic_mode</i>value, the permissions<i>op</i>characters "+" and "-" will be interpreted relative to thecurrent file mode creation mask; "+"will cause the bits for the indicated permissions to be cleared in the mask;"-" will cause the bits for the indicated permissions to be setin the mask.The interpretation of<i>mode</i>values that specify file mode bits other than thefile permission bits is unspecified.In the obsolescent octal integer form of<i>mode</i>,the specified bits will be set in the file mode creation mask.The file mode creation mask will be set to the resulting numeric value.The default output of a prior invocation of<i>umask</i>on the same system with nooperand will also be recognised as a<i>mask</i>operand.The use of an operand obtained in this way isnot obsolescent, even if it is an octal number.</dl></blockquote><h4><a name = "tag_001_014_2453"> </a>STDIN</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_2454"> </a>INPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2455"> </a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables affect the execution of<i>umask</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).<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_2456"> </a>ASYNCHRONOUS EVENTS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_2457"> </a>STDOUT</h4><blockquote>When the<i>mask</i>operand is not specified, the<i>umask</i>utility will write a message to standard outputthat can later be used as a<i>umask</i><i>mask</i>operand.<p>If<b>-S</b>is specified, the message will be in the following format:<p><code><pre><tt>"u=%s,g=%s,o=%s\n"</tt>, <<i>owner permissions</i>>,<<i>group permissions</i>>,<<i>other permissions</i>></pre></code>where the three values will be combinations of letters from the set{r,w,x};the presence of a letter will indicate that the corresponding bit is clearin the file mode creation mask.<p>If a<i>mask</i>operand is specified,there will be no output written to standard output.</blockquote><h4><a name = "tag_001_014_2458"> </a>STDERR</h4><blockquote>Used only for diagnostic messages.</blockquote><h4><a name = "tag_001_014_2459"> </a>OUTPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2460"> </a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2461"> </a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd>The file mode creation mask was successfully changed, or no<i>mask</i>operand was supplied.<dt>>0<dd>An error occurred.</dl></blockquote><h4><a name = "tag_001_014_2462"> </a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_2463"> </a>APPLICATION USAGE</h4><blockquote>Since<i>umask</i>affects the current shell execution environment,it is generally provided as a shell regular built-in.<p>In contrast to the negative permission logic provided by thefile mode creation mask and the octal number form of the<i>mask</i>argument,the symbolic form of the<i>mask</i>argument specifies those permissions that are left alone.<p>The references to octal modes are supportedbecause, although they are obsolescent in the ISO/IEC 9945-2:1993 standard,XSI-conformant systems have committed to maintaining themfor portable applications until further notice.</blockquote><h4><a name = "tag_001_014_2464"> </a>EXAMPLES</h4><blockquote>Either of the commands:<pre><code>umask a=rx,ug+wumask 002</code></pre>sets the mode mask so that subsequently created files have theirS_IWOTHbit cleared.<p>After setting the mode mask with either of the above commands, the<i>umask</i>command can be used to write out the current value of the mode mask:<pre><code><b>$ </b>umask<b>0002</b></code></pre><p>(The output format isunspecified, but historical implementations use the obsolescent octalinteger mode format.)<pre><code><b>$ </b>umask -S<b>u=rwx,g=rwx,o=rx</b></code></pre><p>Either of these outputs can be used as the mask operandto a subsequent invocation of the<i>umask</i>utility.<p>Assuming the mode mask is set as above, the command:<pre><code>umask g-w</code></pre>sets the mode mask so that subsequently created files have theirS_IWGRP,andS_IWOTHbits cleared.<p>The command:<pre><code>umask -- -w</code></pre><p>sets the mode mask so that subsequently created files have all their writebits cleared.Note that<i>mask</i>operands<b>-r</b>,<b>-w</b>,<b>-x</b>or anything beginningwith a hyphen, must be preceded by--to keep it from being interpreted as an option.</blockquote><h4><a name = "tag_001_014_2465"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2466"> </a>SEE ALSO</h4><blockquote><i><a href="chmod.html">chmod</a></i>,the <b>XSH</b> specification description of<i><a href="../xsh/umask.html">umask()</a></i>.<br></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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