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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>test</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_2258"> </a>NAME</h4><blockquote>test - evaluate expression</blockquote><h4><a name = "tag_001_014_2259"> </a>SYNOPSIS</h4><blockquote><pre><code>test <b>[</b><i>expression</i><b>]</b>[ <b>[</b><i>expression</i><b>]</b> ]</code></pre></blockquote><h4><a name = "tag_001_014_2260"> </a>DESCRIPTION</h4><blockquote>The<i>test</i>utility evaluates the<i>expression</i>and indicates the resultof the evaluation by its exit status.An exit status of zero indicatesthat the expression evaluated as true and an exit status of 1 indicatesthat the expression evaluated as false.<p>In the second form of the utility,which uses [] rather than<i>test</i>,the square brackets must be separate arguments.</blockquote><h4><a name = "tag_001_014_2261"> </a>OPTIONS</h4><blockquote>The<i>test</i>utility does not recognise the--argument in the manner specified by guideline 10 inthe <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b> </a> .<p>No options are supported.</blockquote><h4><a name = "tag_001_014_2262"> </a>OPERANDS</h4><blockquote>All operators and elements of primariesmust be presented as separate arguments to the<i>test</i>utility.<p>The following primaries can be used to construct<i>expression</i>:<dl compact><dt><b>-b </b><i>file</i><dd>True if<i>file</i>exists and is a block special file.<dt><b>-c </b><i>file</i><dd>True if<i>file</i>exists and is a character special file.<dt><b>-d </b><i>file</i><dd>True if<i>file</i>exists and is a directory.<dt><b>-e </b><i>file</i><dd>True if<i>file</i>exists.<dt><b>-f </b><i>file</i><dd>True if<i>file</i>exists and is a regular file.<dt><b>-g </b><i>file</i><dd>True if<i>file</i>exists and its set group ID flag is set.<dt><b>-n </b><i>string</i><dd>True if the length of<i>string</i>is non-zero.<dt><b>-p </b><i>file</i><dd>True if<i>file</i>is a named pipe (FIFO).<dt><b>-r </b><i>file</i><dd>True if<i>file</i>exists and is readable.<dt><b>-s </b><i>file</i><dd>True if<i>file</i>exists and has a size greater than zero.<dt><b>-t </b><i>file_descriptor</i><dd>True if the file whose file descriptor number is<i>file_descriptor</i>is open and is associated with a terminal.<dt><b>-u </b><i>file</i><dd>True if<i>file</i>exists and its set-user-ID flag is set.<dt><b>-w </b><i>file</i><dd>True if<i>file</i>exists and is writable.True will indicate only that the write flag is on.The<i>file</i>will not be writable on a read-only file systemeven if this test indicates true.<dt><b>-x </b><i>file</i><dd>True if<i>file</i>exists and is executable.True will indicate only that the execute flag is on.If<i>file</i>is a directory, true indicates that<i>file</i>can be searched.<dt><b>-z </b><i>string</i><dd>True if the length of string<i>string</i>is zero.<dt><i>string</i><dd>True if the string<i>string</i>is not the null string.<dt><i>s1 </i><b>= </b><i>s2</i><dd>True if the strings<i>s1</i>and<i>s2</i>are identical.<dt><i>s1 </i><b>!= </b><i>s2</i><dd>True if the strings<i>s1</i>and<i>s2</i>are not identical.<dt><i>n1 </i><b>-eq </b><i>n2</i><dd>True if the integers<i>n1</i>and<i>n2</i>are algebraically equal.<dt><i>n1 </i><b>-ne </b><i>n2</i><dd>True if the integers<i>n1</i>and<i>n2</i>are not algebraically equal.<dt><i>n1 </i><b>-gt </b><i>n2</i><dd>True if the integer<i>n1</i>is algebraically greater than the integer<i>n2</i>.<dt><i>n1 </i><b>-ge </b><i>n2</i><dd>True if the integer<i>n1</i>is algebraically greater than or equal to the integer<i>n2.</i><dt><i>n1 </i><b>-lt </b><i>n2</i><dd>True if the integer<i>n1</i>is algebraically less than the integer<i>n2</i>.<dt><i>n1 </i><b>-le </b><i>n2</i><dd>True if the integer<i>n1</i>is algebraically less than or equal to the integer<i>n2</i>.<dt><i>expression1</i> <b>-a</b> <i>expression2</i><dd>True if both<i>expression1</i>and<i>expression2</i>are true.The<b>-a</b>binary primary is left associative.It has a higher precedence than<b>-o</b>.<dt><i>expression1</i> <b>-o</b> <i>expression2</i><dd>True if either<i>expression1</i>or<i>expression2</i>is true.The<b>-o</b>binary primary is left associative.</dl><p>These primaries can be combined with the following operators:<dl compact><dt><b>! </b><i>expression</i><dd>True if<i>expression</i>is false.<dt><b>( </b><i>expression </i><b>)</b><dd>True if<i>expression</i>is true.The parenthesescan be used to alter the normal precedence and associativity.</dl><p><p>The primaries with two elements of the form:<p><code><b>-</b><i>primary_operator</i><i>primary_operand</i></code><br>are known as<i>unary primaries.</i>The primaries with three elements in either of the two forms:<p><code><i>primary_operand</i><b>-</b><i>primary_operator</i><i>primary_operand</i><p><i>primary_operand</i><i>primary_operator</i><i>primary_operand</i></code><p>are known as<i>binary primaries.</i>Additional implementation-dependent operators and<i>primary_operator</i>smay be provided by implementations.They will be of the form<b>-</b><i>operator</i>where the first character of<i>operator</i>is not a digit.<p>The algorithm for determining the precedence of the operatorsand the return value that will be generatedis based on the number of arguments presented to<i>test</i>.(However, when using the[...]form, the right-bracket final argumentwill not be counted in this algorithm.)<p>In the following list,$1,$2,$3and$4represent the arguments presented to<i>test</i>.<dl compact><dt>0 arguments:<dd>Exit false (1).<dt>1 argument:<dd>Exit true (0) if$1is not null;otherwise, exit false.<dt>2 arguments:<dd><ul><li>If$1is"!",exit true if$2is null,false if$2is not null.<li>If$1is a unary primary,exit true if the unary test is true,false if the unary test is false.<li>Otherwise, produce unspecified results.</ul><dt>3 arguments:<dd><ul><li>If$2is a binary primary,perform the binary test of$1and$3.<li>If$1is"!",negate the two-argument test of$2and$3.<li>If$1is"("and$3is")",perform the unary test of$2.<li>Otherwise, produce unspecified results.</ul><dt>4 arguments:<dd><ul><li>If$1is"!",negate the three-argument test of$2,$3and$4.<li>If$1is"("and$4is")",perform the two-argument test of$2and$3.<li>Otherwise, the results are unspecified.</ul><dt>>4 arguments:<dd>Combinations of primaries and operatorsare evaluated using the precedence and associativity rulesdescribed previously.In addition, the string comparison binary primaries "=" and!=have a higher precedence than any unary primary.</dl></blockquote><h4><a name = "tag_001_014_2263"> </a>STDIN</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_2264"> </a>INPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2265"> </a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables affect the execution of<i>test</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_2266"> </a>ASYNCHRONOUS EVENTS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_2267"> </a>STDOUT</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_2268"> </a>STDERR</h4><blockquote>Used only for diagnostic messages.</blockquote><h4><a name = "tag_001_014_2269"> </a>OUTPUT FILES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2270"> </a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_2271"> </a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd><i>expression</i>evaluated to true.<dt>1<dd><i>expression</i>evaluated to false or<i>expression</i>was missing.<dt>>1<dd>An error occurred.</dl></blockquote><h4><a name = "tag_001_014_2272"> </a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_2273"> </a>APPLICATION USAGE</h4><blockquote>Scripts should be careful when dealing with user-suppliedinput that could be confused with primaries and operators.Unless the application writer knows all the casesthat produce input to the script, invocations like:<pre><code>test "$1" -a "$2"</code></pre>should be written as:<pre><code>test "$1" && test "$2"</code></pre>to avoid problems if a user supplied values such as$1set to"!"and$2set to the null string.That is, in cases where maximal portability is of concern, replace:<pre><code>test expr1 -a expr2</code></pre>with:<pre><code>test expr1 && test expr2</code></pre>and replace:<pre><code>test expr1 -o expr2</code></pre>with:<pre><code>test expr1 || test expr2</code></pre>but note that, in<i>test</i>,<b>-a</b>has higher precedence than<b>-o</b>while&&and||have equal precedence in the shell.<p>Parentheses or braces can be usedin the shell command language to effect grouping.<p>Parentheses must be escaped when using<i><a href="sh.html">sh</a></i>;for example:<pre><code>test \( expr1 -a expr2 \) -o expr3</code></pre><p>This command is not always portable outside XSI-conformant systems.The following form can be used instead:<pre><code>( test expr1 && test expr2 ) || test expr3</code></pre><p>The two commands:<pre><code>test "$1"test ! "$1"</code></pre>could not be used reliably on some historical systems.Unexpected results would occur if such a<i>string</i>expression were used and$1expanded to "!", "(" or a known unary primary.Better constructs are:<pre><code>test -n "$1"test -z "$1"</code></pre>respectively.<p>Historical systems have also been unreliable given thecommon construct:<pre><code>test "$response" = "expected string"</code></pre>One of the following is a more reliable form:<pre><code>test "X$response" = "Xexpected string"test "expected string" = "$response"</code></pre><p>Note that the second form assumes thatexpected stringcould not be confused with any unary primary.Ifexpected stringstarts with "-", "(", "!"or even "=", the first form should be used instead.Using the preceding rules without the marked extensions,any of the three comparisonforms is reliable, given any input.(However, note that the strings are quoted in all cases.)<p>Because the string comparison binary primaries,"="and!=,have a higher precedence than any unary primary in the greater than4 argument case,unexpected results can occur if arguments are not properly prepared.For example, in:<pre><code>test -d $1 -o -d $2</code></pre><p>If$1evaluates to a possible directory name of <b>=</b>,the first three arguments are considered a string comparison,which causes a syntax error when the second<b>-d</b>is encountered.One of the following forms prevents this; the second is preferred:<pre><code>test \( -d "$1" \) -o \( -d "$2" \)test -d "$1" || test -d "$2"</code></pre><p>Also in the greater than 4 argument case:<pre><code>test "$1" = "bat" -a "$2" = "ball"</code></pre>Syntax errors will occur if$1evaluates to "(" or "!".One of the following forms prevents this; the third is preferred:<pre><code>test "X$1" = "Xbat" -a "X$2" = "Xball"test "$1" = "bat" && test "$2" = "ball"test "X$1" = "Xbat" && test "X$2" = "Xball"</code></pre><br></blockquote><h4><a name = "tag_001_014_2274"> </a>EXAMPLES</h4><blockquote><ol><p><li>Exit if there are not two or three arguments (two variations):<pre><code>if [ $# -ne 2 -a $# -ne 3 ]; then exit 1; fi if [ $# -lt 2 -o $# -gt 3 ]; then exit 1; fi </code></pre><br><p><li>Perform a<i><a href="mkdir.html">mkdir</a></i>if a directory does not exist:<pre><code>test ! -d tempdir && mkdir tempdir</code></pre><p><li>Wait for a file to become non-readable:<pre><code>while test -r thefiledo sleep 30doneecho '"thefile" is no longer readable'</code></pre><p><li>Perform a command if the argument is one of three strings (two variations):<pre><code>if [ "$1" = "pear" ] || [ "$1" = "grape" ] || [ "$1" = "apple" ]then <i>command</i>ficase "$1" in pear|grape|apple) <i>command</i> ;;esac</code></pre><p></ol></blockquote><h4><a name = "tag_001_014_2275"> </a>FUTURE DIRECTIONS</h4><blockquote>The IEEE PASC 1003.2 Interpretations Committee has forwarded concerns aboutparts of this interface definition to the IEEE PASC Shell and Utilities Working Groupwhich is identifying the corrections.A future revision of this specification will align withIEEE Std. 1003.2b when finalised.</blockquote><h4><a name = "tag_001_014_2276"> </a>SEE ALSO</h4><blockquote><i><a href="find.html">find</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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