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11 KiB
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tools", lightened and sepia-toned. Over this was placed a Mac Terminal app with
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very light-grey font and translucent background, in which a few statistical
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Miller commands were run with pretty-print-tabular output format.
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<body background="pix/sepia-overlay.jpg">
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<table width="100%">
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<center><titleinbody>Miller</titleinbody></center>
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<!-- PAGE LIST GENERATED FROM template.html BY poki -->
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<br/>• <a href="index.html">About Miller</a>
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<br/>• <a href="file-formats.html"><b>File formats</b></a>
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<br/>• <a href="feature-comparison.html">Miller features in the context of the Unix toolkit</a>
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<br/>• <a href="record-heterogeneity.html">Record-heterogeneity</a>
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<br/>• <a href="reference.html">Reference</a>
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<br/>• <a href="data-examples.html">Data examples</a>
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<br/>• <a href="internationalization.html">Internationalization</a>
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<br/>• <a href="build.html">Compiling, portability, dependencies, and testing</a>
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<br/>• <a href="performance.html">Performance</a>
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<br/>• <a href="whyc.html">Why C?</a>
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<br/>• <a href="etymology.html">Why call it Miller?</a>
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<br/>• <a href="originality.html">How original is Miller?</a>
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<br/>• <a href="to-do.html">Things to do</a>
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<br/>• <a href="contact.html">Contact information</a>
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<br/>• <a href="https://github.com/johnkerl/miller">GitHub repo</a>
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<br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/>
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<br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/> <br/>
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<br/> <br/> <br/> <br/> <br/> <br/>
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</div>
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</td>
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<!-- page body -->
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<td>
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<div style="overflow-y:scroll;height:1500px">
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<center> <titleinbody> File formats </titleinbody> </center>
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<p/>
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<!-- BODY COPIED FROM content-for-file-formats.html BY poki -->
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<div class="pokitoc">
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<center><b>Contents:</b></center>
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• <a href="#CSV/TSV/etc.">CSV/TSV/etc.</a><br/>
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• <a href="#Pretty-printed">Pretty-printed</a><br/>
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• <a href="#Key-value_pairs">Key-value pairs</a><br/>
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• <a href="#Index-numbered_(toolkit_style)">Index-numbered (toolkit style)</a><br/>
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• <a href="#Vertical_tabular">Vertical tabular</a><br/>
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</div>
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<p/>
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<a id="CSV/TSV/etc."/><h1>CSV/TSV/etc.</h1>
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When <tt>mlr</tt> is invoked with the <tt>--csv</tt> or <tt>--csvlite</tt> option,
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key names are found on the first record and values are taken from subsequent
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records. This includes the case of CSV-formatted files. See
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<a href="record-heterogeneity.html">Record-heterogeneity</a> for how Miller handles
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changes of field names within a single data stream.
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<p/> Miller has record separator <tt>RS</tt> and field separator <tt>FS</tt>,
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just as <tt>awk</tt> does. For TSV, use <tt>--fs tab</tt>; to convert TSV to
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CSV, use <tt>--ifs tab --ofs comma</tt>, etc. (See also
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<a href="reference.html">Reference</a>.)
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<p/>Miller’s <tt>--csv</tt> flag supports RFC-4180 CSV (<a href="https://tools.ietf.org/html/rfc4180">
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https://tools.ietf.org/html/rfc4180</a>). This includes CRLF line-terminators by default, regardless
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of platform. You can use <tt>mlr --csv --rs lf</tt> for native Un*x (LF-terminated) CSV files.
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<a id="Pretty-printed"/><h1>Pretty-printed</h1>
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Miller’s pretty-print format is like CSV, but column-aligned. For example, compare
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<table><tr><td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr --ocsv cat data/small
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a,b,i,x,y
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pan,pan,1,0.3467901443380824,0.7268028627434533
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eks,pan,2,0.7586799647899636,0.5221511083334797
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wye,wye,3,0.20460330576630303,0.33831852551664776
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eks,wye,4,0.38139939387114097,0.13418874328430463
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wye,pan,5,0.5732889198020006,0.8636244699032729
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</pre>
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</div>
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<p/>
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</td>
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<td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr --opprint cat data/small
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a b i x y
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pan pan 1 0.3467901443380824 0.7268028627434533
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eks pan 2 0.7586799647899636 0.5221511083334797
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wye wye 3 0.20460330576630303 0.33831852551664776
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eks wye 4 0.38139939387114097 0.13418874328430463
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wye pan 5 0.5732889198020006 0.8636244699032729
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</pre>
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</div>
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<p/>
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</td></tr></table>
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Note that while Miller is a line-at-a-time processor and retains input lines in
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memory only where necessary (e.g. for sort), pretty-print output requires it to
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accumulate all input lines (so that it can compute maximum column widths)
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before producing any output. This has two consequences: (a) pretty-print output
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won’t work on <tt>tail -f</tt> contexts, where Miller will be waiting for
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an end-of-file marker which never arrives; (b) pretty-print output for large
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files is constrained by available machine memory.
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<p/> See <a href="record-heterogeneity.html">Record-heterogeneity</a> for how Miller
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handles changes of field names within a single data stream.
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<a id="Key-value_pairs"/><h1>Key-value pairs</h1>
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Miller’s default file format is DKVP, for <b>delimited key-value pairs</b>. Example:
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr cat data/small
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a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
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a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
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a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
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a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
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a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
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</pre>
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</div>
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<p/>
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Such data are easy to generate, e.g. in Ruby with
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<p/>
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<div class="pokipanel">
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<pre>
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puts "host=#{hostname},seconds=#{t2-t1},message=#{msg}"
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</pre>
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</div>
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<p/>
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<p/>
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<div class="pokipanel">
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<pre>
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puts mymap.collect{|k,v| "#{k}=#{v}"}.join(',')
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</pre>
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</div>
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<p/>
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or <tt>print</tt> statements in various languages, e.g.
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<p/>
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<div class="pokipanel">
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<pre>
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echo "type=3,user=$USER,date=$date\n";
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</pre>
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</div>
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<p/>
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<p/>
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<div class="pokipanel">
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<pre>
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logger.log("type=3,user=$USER,date=$date\n");
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</pre>
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</div>
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<p/>
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<p/> As discussed in <a href="record-heterogeneity.html">Record-heterogeneity</a>, Miller handles
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changes of field names within the same data stream. But using DKVP format this is particularly
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natural. One of my favorite use-cases for Miller is in application/server logs, where I log all sorts
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of lines such as
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<p/>
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<div class="pokipanel">
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<pre>
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resource=/path/to/file,loadsec=0.45,ok=true
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record_count=100, resource=/path/to/file
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resource=/some/other/path,loadsec=0.97,ok=false
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</pre>
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</div>
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<p/>
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etc. and I just log them as needed. Then later, I can use <tt>grep</tt>, <tt>mlr --opprint group-like</tt>, etc.
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to analyze my logs.
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<p/>See <a href="reference.html">Reference</a> regarding how to specify separators other than
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the default equals-sign and comma.
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<a id="Index-numbered_(toolkit_style)"/><h1>Index-numbered (toolkit style)</h1>
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With <tt>--inidx --ifs ' ' --repifs</tt>, Miller splits lines on whitespace and
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assigns integer field names starting with 1. This recapitulates Unix-toolkit
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behavior.
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<p/> Example with index-numbered output:
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<table><tr> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ cat data/small
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a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
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a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
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a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
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a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
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a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
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</pre>
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</div>
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<p/>
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</td> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr --onidx --ofs ' ' cat data/small
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pan pan 1 0.3467901443380824 0.7268028627434533
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eks pan 2 0.7586799647899636 0.5221511083334797
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wye wye 3 0.20460330576630303 0.33831852551664776
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eks wye 4 0.38139939387114097 0.13418874328430463
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wye pan 5 0.5732889198020006 0.8636244699032729
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</pre>
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</div>
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<p/>
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</td> </tr></table>
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<p/> Example with index-numbered input:
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<table><tr> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ cat data/mydata.txt
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oh say can you see
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by the dawn's
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early light
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</pre>
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</div>
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<p/>
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</td> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr --inidx --ifs ' ' --odkvp cat data/mydata.txt
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1=oh,2=say,3=can,4=you,5=see
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1=by,2=the,3=dawn's
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1=early,2=light
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</pre>
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</div>
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<p/>
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</td> </tr></table>
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<p/> Example with index-numbered input and output:
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<table><tr> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ cat data/mydata.txt
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oh say can you see
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by the dawn's
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early light
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</pre>
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</div>
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<p/>
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</td> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ mlr --nidx --fs ' ' --repifs cut -f 2,3 data/mydata.txt
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say can
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the dawn's
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light
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</pre>
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</div>
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<p/>
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</td> </tr></table>
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<a id="Vertical_tabular"/><h1>Vertical tabular</h1>
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<p/>This is perhaps most useful for looking a very wide and/or multi-column
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data which causes line-wraps on the screen (but see also <a
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href="https://github.com/twosigma/ngrid">https://github.com/twosigma/ngrid</a>
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for an entirely different, very powerful option). Namely:
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<table><tr> <td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ grep -v '^#' /etc/passwd | head -n 6 | mlr --nidx --fs : --opprint cat
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1 2 3 4 5 6 7
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nobody * -2 -2 Unprivileged User /var/empty /usr/bin/false
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root * 0 0 System Administrator /var/root /bin/sh
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daemon * 1 1 System Services /var/root /usr/bin/false
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_uucp * 4 4 Unix to Unix Copy Protocol /var/spool/uucp /usr/sbin/uucico
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_taskgated * 13 13 Task Gate Daemon /var/empty /usr/bin/false
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_networkd * 24 24 Network Services /var/networkd /usr/bin/false
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</pre>
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</div>
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<p/>
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</td></tr> <tr><td>
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<p/>
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<div class="pokipanel">
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<pre>
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$ grep -v '^#' /etc/passwd | head -n 2 | mlr --nidx --fs : --oxtab cat
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1 nobody
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2 *
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3 -2
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4 -2
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5 Unprivileged User
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6 /var/empty
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7 /usr/bin/false
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1 root
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2 *
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3 0
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4 0
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5 System Administrator
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6 /var/root
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7 /bin/sh
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</pre>
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</div>
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<p/>
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</td> </tr></table>
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</div>
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</td>
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</table>
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</body>
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</html>
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