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POHow to make grep stop at first match on a line?
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  1. POHow to make grep stop at first match on a line?
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    copied!<p>Well, I have a file test.txt</p> <pre> #test.txt odsdsdoddf112 test1_for_grep dad23392eeedJ test2 for grep Hello World test garbage </pre> <p>I want to extract strings which have got a space after them. I used following expression and it worked</p> <pre> grep -o [[:alnum:]]*.[[:blank:]] test.txt </pre> <p>Its output is </p> <pre> odsdsdoddf112 dad23392eeedJ test2 for Hello World </pre> <p>But problem is grep prints all the strings that have got space after them, where as I want it to stop after first match on a line and then proceed to second line.</p> <p>Which expression should I use here, in order to make it stop after first match and move to next line?</p> <p>This problem may be solved with gawk or some other tool, but I will appreciate a solution which uses grep only.</p> <p><strong>Edit</strong> I using GNU grep 2.5.1 on a Linux system, if that is relevant. </p> <p><strong>Edit</strong></p> <p>With the help of the answers given below, I tried my luck with </p> <pre> grep -o ^[[:alnum:]]* test.txt grep -Eo ^[[:alnum:]]+ test.txt </pre> <p>and both gave me correct answers. </p> <p>Now what surprises me is that I tried using </p> <pre> grep -Eo "^[[:alnum:]]+[[:blank:]]" test.txt </pre> <p>as suggested <a href="https://stackoverflow.com/questions/1495229/how-to-make-grep-stop-at-first-match-on-a-line/1495253#1495253">here</a> but didn't get the correct answer. Here is the output on my terminal</p> <pre> odsdsdoddf112 dad23392eeedJ test2 for Hello World </pre> <p>But comments from RichieHindle and Adrian Pronk, shows that they got correct output on their systems. Anyone with some idea that why I too am not getting the same result on my system. Any idea? Any help will be appreciated.</p> <p><strong>Edit</strong></p> <p>Well, it seems that grep 2.5.1 has some bug because of which my output wasn't correct. I installed grep 2.5.4, now it is working correctly. Please see <a href="http://www.linuxquestions.org/questions/linux-newbie-8/why-this-grep-command-with-regular-expressions-not-working-on-my-system-758692/" rel="nofollow noreferrer">this link</a> for details.</p>
 

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