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POBash: read a file line-by-line and process each segment as parameters to other prog
 

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  1. POBash: read a file line-by-line and process each segment as parameters to other prog
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    <p>I have some dirty work to do, so a Bash script seems to be a good choice. I'm new to Bash, and the experience makes me kind of frustrated.</p> <p>The file mapfiles.txt consists of lines as follow. Each line has four segments separated by a white space. Each segment represents a input parameter to an external program name 'prog'. For example, "cm19_1.png" is the <strong>filename</strong>, "0001" the <strong>index</strong>, "121422481" the <strong>longitude</strong>, and "31035995" the <strong>latitude</strong>.</p> <p>File: mapfiles.txt</p> <pre><code>cm19_1.png 0001 121422481 31035995 cm19_2.png 0002 121423224 31035995 cm19_3.png 0003 121423967 31035995 … </code></pre> <p>I want to execute similar commands to each line. As show below, the prog's input parameter order is slightly different. So it makes sense to write a bash script to handle the repeated work.</p> <pre><code>[Usage] prog &lt;index&gt; &lt;longitude&gt; &lt;latitude&gt; &lt;filename&gt; example: prog 0001 121422481 31035995 cm19_1.png </code></pre> <p>Generally, the bash script will operate in this way: </p> <ol> <li>Read one line from mapfiles.txt</li> <li>Split the segments</li> <li>Call the prog with a correct parameter order</li> </ol> <p>Here comes run.sh.</p> <pre><code>#!/bin/sh input=mapfiles.txt cmd=prog while read line do file=$(echo $line | cut -d' ' -f1) key=$(echo $line | cut -d' ' -f2) log=$(echo $line | cut -d' ' -f3) lat=$(echo $line | cut -d' ' -f4) echo $cmd $key $log $lat $file done &lt; "$input" </code></pre> <p>What I expected is</p> <pre><code>prog 0001 121422481 31035995 cm19_1.png prog 0002 121423224 31035995 cm19_2.png prog 0003 121423967 31035995 cm19_3.png … </code></pre> <p>The ACTUAL result I got is</p> <pre><code> cm19_1.png21422481 31035995 cm19_2.png21423224 31035995 cm19_3.png21423967 31035995 </code></pre> <p>Problems that confused me</p> <ol> <li>Where is 'prog'? </li> <li>Where is the white space?</li> <li>What's wrong with the parameter order?</li> </ol> <p>Hmm… I wrote this script on my Mac using vim and copy it to a Scientific Linux box and a gentoo box. These three guys get the same ridiculous outputs.</p>
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    1. CONot reproducible here. Look for typos. Also, instead of all the cuts use just `read file key log lat`. *UPD* see the answer.
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    2. COWhen combined with ssh in the loop, take a look at this question: http://stackoverflow.com/questions/9393038/ssh-breaks-out-of-while-loop-in-bash
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