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    <p>Why are so many people invoking <code>grep</code> in the pipeline and either using <code>bash</code>'s <code>for</code> loops or <code>xargs</code> on the back end when they have bloody <strong><code>awk</code></strong> right in the middle of things?</p> <p>First let's get rid of the whimsical use of grep:</p> <pre><code>svn st | awk '/^?/ { print $2 }' </code></pre> <p>Since <code>awk</code> allows you to filter lines based on regular expressions, the use of grep is entirely unnecessary. The regular expressions of <code>awk</code> aren't that different from <code>grep</code> (depending on which implementation of <code>awk</code> and which of <code>grep</code> you're using) so why add a whole new process and a whole new bottleneck in the pipeline?</p> <p>From there you already have two choices that would be shorter and more readable:</p> <pre><code># option 1 svn st | awk '/^?/ { print $2 }' | xargs rm -f # option 2 rm -f $(svn st | awk '/^?/ { print $2 }') </code></pre> <p>Now that second option will only work if your file list doesn't exceed the maximum command line size, so I recommend the xargs version.</p> <p>Or, perhaps even better, use <code>awk</code> again.</p> <pre><code>svn st | awk '/^?/ { system("rm -f $2") }' </code></pre> <p>This will be the functional equivalent of what you did above with the <code>for</code> loop. It's grotesquely inefficient, seeing as it will execute rm once per file, but it's at least more readable than your <code>for</code> loop example. It can be improved still farther, however. I won't go into full details here, but will instead give you comments as clues as to what the final solution would look like.</p> <pre><code>svn st | awk 'BEGIN{ /*set up an array*/ }; /^?/ { /*add $2 to the array*/ }; END{ /*system("rm -f ...") safe chunks of the array*/} </code></pre> <p>OK, so that last one is a bit of a mouthful and too much to type off as a routine one-liner. Since you have to "often" do this, however, it shouldn't be too bad to put this into a script:</p> <pre><code>#!/usr/bin/env awk BEGIN { /* set up your accumulator array */ } /^?/ { /* add $2 to the array */ } END { /* invoke system("rm -f") on safe chunks of the accumulator array */ } </code></pre> <p>Now your command line will be <code>svn st | myawkscript</code>.</p> <p>Now I'll warn you I'm not equipped to check all this (since I avoid SVN and CVS like I avoid MS-DOS -- and for much the same reason). You might have to monkey with the <code>#!</code> line in the script, for example, or with the regular expression you use to filter, but the general principle remains about the same. And me personally? I'd use <code>svn st | awk '/^?/ { print $2 }' | xargs rm -f</code> for something I do infrequently. I'd only do the full script for something I do several times a week or more.</p>
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    1. POHow to express "map a linux command to each line in a file"?
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    1. USJUST MY correct OPINION
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    1. POHow to express "map a linux command to each line in a file"?
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    1. COThis is wonderful!
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    2. COIt seems the END expression will feed the list of file paths to "rm -f". In this case, would it suffer the problem that the list of arguments might exceed the maximum command line size?
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    3. COHence the reference to "safe chunks". You put in a loop that grabs less than the maximum command line size at a time and issue `rm -f`. `awk` is a general-purpose programming language. It has loops and conditionals and calculations and all sorts of nifty stuff beyond pattern matching.
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