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    <p>Are you sure that all the files really show up in <code>cat *.txt &gt; out</code>? Unless you are right at the edge of the maximum number of characters per command, it should not make a difference. Try this:</p> <pre><code>ls -1 | egrep '\.txt$' | xargs egrep "" /dev/null &gt; out </code></pre> <p><code>ls -1</code> lists all the files in the directory, one file name per line, and the first <code>egrep</code> filters out just the ones ending in ".txt". This way, you don't have to worry about running out of command line length in listing the files. <code>xargs</code> reads <code>stdin</code>, until it gets as many lines as it can fit on a single command line after the other arguments to <code>xargs</code>. It then calls the command you provide with the options you provided with that set of input parameters. <code>xargs</code> then repeats that process until it uses up all the arguments you provide. Each invocation of the final <code>egrep</code> writes to the same <code>stdout</code>, so all the output goes to the same file.</p> <p>The <code>/dev/null</code> is there in case <code>xargs</code> only finds one line of input (for example, becuase you only have one file or when bundling up files, the last bundle only has one file). If you call <code>egrep</code> with a single file, it does not print the file name. Since you specifically said you want the file names, telling <code>egrep</code> to search <code>/dev/null</code> guarantees there will always be at least two files. Since <code>/dev/null</code> is guaranteed to be empty, you will never find anything in it, and it will not show up in your output.</p> <p><code>xargs</code> works great with <code>find</code>. If you wanted to search for "foo" in all the ".txt" files in the current directory and its subdirectories:</p> <pre><code>find . -name "*.txt" -print | xargs egrep foo /dev/null </code></pre> <p>would do the trick. If you have file names with spaces in them, they won't get quoted and <code>egrep</code> will get confused, so use the <code>-print0</code> option on <code>find</code> and the <code>-0</code> option on xargs:</p> <pre><code>find . -name "*.txt" -print0 | xargs -0 egrep foo /dev/null </code></pre>
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    1. PODoes "grep" have maximum of files it can handle?
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    1. USwrdieter
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    1. PODoes "grep" have maximum of files it can handle?
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    1. VO
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    1. COIf you add the `-H` flag to `egrep` you'll be able to drop the `/dev/null` argument.
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      1. USiscfrc
    2. CO@iscfrc Good tip. I learned the /dev/null trick a number of years ago on a version of grep that did not have -H.
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