use Perl

• Various improvements (Score:1)

  by Aristotle (5147) <pagaltzis@gmx.de> on 2007.03.05 22:37 (#53502) Homepage Journal

  Unlike sh, bash has arithmetic evaluation that would make your script much simpler. I also wouldn’t check for the dotfile’s existence, just read it with error messages suppressed. It’s also bizarre that you’re using date +%s to get the timestamp in one place and perl -e 'print time' in another – and the backticks around that second place are even more so. All in all here’s how I’d write that:

  #!/usr/local/bin/bash
  
  [ -r ~/.bashrc ] && source ~/.bashrc
  
  timestamp=.login_time
  
  cd /home/cpoe/work/main/
  
  last_time=$( cat "$timestamp" 2>&- )
  curr_time=$( date +%s )
  
  if (( curr_time - last_time > 600 ))  # five (???) minutes
  then
      echo "$curr_time" > "$timestamp"
      /usr/bin/cvs up -d
      /usr/local/bin/runtests -lr
  fi

  But actually, “run the tests if it’s been 5 minutes since my last login” strikes me as a hack. I think what you rather want to say is “skip the tests if cvs up didn’t find any updates to pull.” That would look something like this:

  #!/usr/local/bin/bash
  
  [ -r ~/.bashrc ] && source ~/.bashrc
  
  timestamp=.login_time
  
  cd /home/cpoe/work/main/
  
  tmp=$( mktemp ) && {
      /usr/bin/cvs up -d | tee "$tmp"
      [ -s "$tmp" ] && /usr/local/bin/runtests -lr
      rm -f "$tmp"
  }

  This is based on the fact that cvs prints its U foo/bar.c lines to stdin, but its chatter to stderr. So it copies cvs’s stdout to a temporary file whose size will be nonzero only if cvs actually did any updates. The tests run only if that’s the case.

  Reply to This

  • Re: (Score:2)

    by Ovid (2709)

    By the way, I did implement many of your suggestions, thank you. However, I deliberately didn't want to go with the 'don't run tests if there are no updates to CVS'. There are plenty of other ways -- admittedly less common -- that tests can fail even without CVS updates. When those failures occur, I'd like to catch them!
    • Re: (Score:1)

      by Aristotle (5147)

      Ah. Btw, a much more direct way to do this just occured to me: use the file’s mtime.

      #!/usr/local/bin/bash
      
      [ -r ~/.bashrc ] && source ~/.bashrc
      
      timestamp=.login_time
      
      cd /home/cpoe/work/main/
      
      if [[ `find "$timestamp" -mmin +5 -print` ]] ; then
          touch "$timestamp"
          /usr/bin/cvs up -d
          /usr/local/bin/runtests -lr
      fi

      The idiomatic bit here is using find to check the file’s age. The -mmin +5 predicate means “if the mtime of the file under considerat