http://www.perlmonks.org?node_id=969515


in reply to Search and replace within a file

Take a look at the -i switch, which does in-place file transformations.

Examples are in my presentation A Field Guide To The Perl Command Line.

xoxo,
Andy

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Re^2: Search and replace within a file
by sriharsha.sm (Initiate) on May 10, 2012 at 13:55 UTC
    I thought of recommending the inplace replace using sed. Sorry for recommending sed over perl here.. But I believe this needs to be done in sed than in perl. 
    $sed -i 's#uname#newname#' /etc/hosts/*

    [download]
    I did some time comparison for both perl and sed and it turns out that sed has better performance 
    $time sed -i 's/sri/harry/' *
sed -i 's/sri/harry/' *  0.00s user 0.01s system 37% cpu 0.016 total

$time perl -pi -e 's/harry/sri/' 
perl -pi -e 's/harry/sri/' *  0.01s user 0.01s system 62% cpu 0.029 to
+tal

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      But I believe this needs to be done in sed than in perl. [...] I did some time comparison for both perl and sed and it turns out that sed has better performance 
      $time sed -i 's/sri/harry/' *
sed -i 's/sri/harry/' *  0.00s user 0.01s system 37% cpu 0.016 total

$time perl -pi -e 's/harry/sri/' 
perl -pi -e 's/harry/sri/' *  0.01s user 0.01s system 62% cpu 0.029 to
+tal

      [download]

      So, you suggest to optimize a one-shot command run every few day, weeks, or months for a total execution speed advantage of 10 milliseconds on your machine, based on one single run of each command? Are you serious?

      (If yes, let me suggest to use a one-letter shell alias for "perl -pi -e". This saves you 10 keystrokes and thus gains you much more than 10 milliseconds, even if you can type really fast.)

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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