356 lines
11 KiB
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356 lines
11 KiB
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<title>uniq</title>
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<basefont size="3"> <a name="uniq"></a> <a name="tag_04_158"></a><!-- uniq -->
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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_158_01"></a>NAME</h4>
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<blockquote>uniq - report or filter out repeated lines in a file</blockquote>
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<h4><a name="tag_04_158_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>uniq</tt> <b>[</b><tt>-c|-d|-u</tt><b>][</b><tt>-f</tt> <i>fields</i><b>][</b><tt>-s</tt>
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<i>char</i><b>][</b><i>input_file</i> <b>[</b><i>output_file</i><b>]]</b></code></p>
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</blockquote>
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<h4><a name="tag_04_158_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>uniq</i> utility shall read an input file comparing adjacent lines, and write one copy of each input line on the output.
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The second and succeeding copies of repeated adjacent input lines shall not be written.</p>
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<p>Repeated lines in the input shall not be detected if they are not adjacent.</p>
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</blockquote>
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<h4><a name="tag_04_158_04"></a>OPTIONS</h4>
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<blockquote>
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<p>The <i>uniq</i> utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/xbd_chap12.html#tag_12_02">Section 12.2, Utility Syntax Guidelines</a>.</p>
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<p>The following options shall be supported:</p>
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<dl compact>
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<dt><b>-c</b></dt>
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<dd>Precede each output line with a count of the number of times the line occurred in the input.</dd>
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<dt><b>-d</b></dt>
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<dd>Suppress the writing of lines that are not repeated in the input.</dd>
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<dt><b>-f </b> <i>fields</i></dt>
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<dd>Ignore the first <i>fields</i> fields on each input line when doing comparisons, where <i>fields</i> is a positive decimal
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integer. A field is the maximal string matched by the basic regular expression:
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<pre>
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<tt>[[:blank:]]*[^[:blank:]]*
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</tt>
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</pre>
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<p>If the <i>fields</i> option-argument specifies more fields than appear on an input line, a null string shall be used for
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comparison.</p>
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</dd>
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<dt><b>-s </b> <i>chars</i></dt>
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<dd>Ignore the first <i>chars</i> characters when doing comparisons, where <i>chars</i> shall be a positive decimal integer. If
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specified in conjunction with the <b>-f</b> option, the first <i>chars</i> characters after the first <i>fields</i> fields shall be
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ignored. If the <i>chars</i> option-argument specifies more characters than remain on an input line, a null string shall be used
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for comparison.</dd>
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<dt><b>-u</b></dt>
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<dd>Suppress the writing of lines that are repeated in the input.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_158_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>input_file</i></dt>
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<dd>A pathname of the input file. If the <i>input_file</i> operand is not specified, or if the <i>input_file</i> is <tt>'-'</tt> ,
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the standard input shall be used.</dd>
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<dt><i>output_file</i></dt>
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<dd>A pathname of the output file. If the <i>output_file</i> operand is not specified, the standard output shall be used. The
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results are unspecified if the file named by <i>output_file</i> is the file named by <i>input_file</i>.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_158_06"></a>STDIN</h4>
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<blockquote>
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<p>The standard input shall be used only if no <i>input_file</i> operand is specified or if <i>input_file</i> is <tt>'-'</tt> . See
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the INPUT FILES section.</p>
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</blockquote>
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<h4><a name="tag_04_158_07"></a>INPUT FILES</h4>
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<blockquote>
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<p>The input file shall be a text file.</p>
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</blockquote>
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<h4><a name="tag_04_158_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>uniq</i>:</p>
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<dl compact>
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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 and input files) and which characters constitute a <blank> in the current
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locale.</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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</dl>
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</blockquote>
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<h4><a name="tag_04_158_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<h4><a name="tag_04_158_10"></a>STDOUT</h4>
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<blockquote>
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<p>The standard output shall be used only if no <i>output_file</i> operand is specified. See the OUTPUT FILES section.</p>
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</blockquote>
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<h4><a name="tag_04_158_11"></a>STDERR</h4>
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<blockquote>
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<p>The standard error shall be used only for diagnostic messages.</p>
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</blockquote>
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<h4><a name="tag_04_158_12"></a>OUTPUT FILES</h4>
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<blockquote>
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<p>If the <b>-c</b> option is specified, the application shall ensure that the output file is empty or each line shall be of the
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form:</p>
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<pre>
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<tt>"%d %s", <</tt><i>number of duplicates</i><tt>>, <</tt><i>line</i><tt>>
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</tt>
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</pre>
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<p>otherwise, the application shall ensure that the output file is empty or each line shall be of the form:</p>
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<pre>
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<tt>"%s", <</tt><i>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_158_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_158_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> 0</dt>
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<dd>The utility executed successfully.</dd>
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<dt>>0</dt>
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<dd>An error occurred.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_158_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_158_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <a href="../utilities/sort.html"><i>sort</i></a> utility can be used to cause repeated lines to be adjacent in the input
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file.</p>
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</blockquote>
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<h4><a name="tag_04_158_17"></a>EXAMPLES</h4>
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<blockquote>
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<p>The following input file data (but flushed left) was used for a test series on <i>uniq</i>:</p>
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<pre>
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<tt>#01 foo0 bar0 foo1 bar1
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#02 bar0 foo1 bar1 foo1
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#03 foo0 bar0 foo1 bar1
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#04
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#05 foo0 bar0 foo1 bar1
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#06 foo0 bar0 foo1 bar1
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#07 bar0 foo1 bar1 foo0
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</tt>
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</pre>
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<p>What follows is a series of test invocations of the <i>uniq</i> utility that use a mixture of <i>uniq</i> options against the
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input file data. These tests verify the meaning of <i>adjacent</i>. The <i>uniq</i> utility views the input data as a sequence of
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strings delimited by <tt>'\n'</tt> . Accordingly, for the <i>fields</i>th member of the sequence, <i>uniq</i> interprets unique or
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repeated adjacent lines strictly relative to the <i>fields</i>+1th member.</p>
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<ol>
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<li>
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<p>This first example tests the line counting option, comparing each line of the input file data starting from the second
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field:</p>
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<pre>
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<tt>uniq -c -f 1 uniq_0I.t
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1 #01 foo0 bar0 foo1 bar1
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1 #02 bar0 foo1 bar1 foo0
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1 #03 foo0 bar0 foo1 bar1
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1 #04
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2 #05 foo0 bar0 foo1 bar1
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1 #07 bar0 foo1 bar1 foo0
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</tt>
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</pre>
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<p>The number <tt>'2'</tt> , prefixing the fifth line of output, signifies that the <i>uniq</i> utility detected a pair of repeated
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lines. Given the input data, this can only be true when <i>uniq</i> is run using the <b>-f 1</b> option (which shall cause
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<i>uniq</i> to ignore the first field on each input line).</p>
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</li>
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<li>
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<p>The second example tests the option to suppress unique lines, comparing each line of the input file data starting from the
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second field:</p>
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<pre>
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<tt>uniq -d -f 1 uniq_0I.t
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#05 foo0 bar0 foo1 bar1
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</tt>
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</pre>
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</li>
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<li>
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<p>This test suppresses repeated lines, comparing each line of the input file data starting from the second field:</p>
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<pre>
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<tt>uniq -u -f 1 uniq_0I.t
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#01 foo0 bar0 foo1 bar1
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#02 bar0 foo1 bar1 foo1
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#03 foo0 bar0 foo1 bar1
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#04
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#07 bar0 foo1 bar1 foo0
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</tt>
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</pre>
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</li>
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<li>
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<p>This suppresses unique lines, comparing each line of the input file data starting from the third character:</p>
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<pre>
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<tt>uniq -d -s 2 uniq_0I.t
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</tt>
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</pre>
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<p>In the last example, the <i>uniq</i> utility found no input matching the above criteria.</p>
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</li>
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</ol>
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</blockquote>
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<h4><a name="tag_04_158_18"></a>RATIONALE</h4>
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<blockquote>
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<p>Some historical implementations have limited lines to be 1080 bytes in length, which does not meet the implied {LINE_MAX}
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limit.</p>
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</blockquote>
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<h4><a name="tag_04_158_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_158_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="comm.html"><i>comm</i></a> , <a href="sort.html"><i>sort</i></a></p>
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</blockquote>
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<h4><a name="tag_04_158_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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<h4><a name="tag_04_158_22"></a>Issue 6</h4>
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<blockquote>
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<p>The obsolescent SYNOPSIS and associated text are removed.</p>
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<p>The normative text is reworded to avoid use of the term "must" for application requirements.</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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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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