title: How to make grep stop at first match on a line?
body: <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>