[boulder.pm] print/exit on error?

[Walter Pienciak]

On Thu, 17 Aug 2000, Robert L. Harris wrote:

>   Every now and then some of the guys around here bring me scripts to look
> at.  Currently I have one that reads through about 250 files with about 
> 100k lines apiece.  Somewhere int he middle, they're getting an error on
> a substr operation, line is too short.
> 
>   What is the cleanest way to make a perl script do something along the line
> or print out a variable (the file it's currently reading), $_, and then
> exit when it gets such an error?  I could check $? or such for error 
> condition and then exit, but is that the best way?
> 
> Robert

Most of the code I actually maintain is littered with debugging lines:

  BEGIN { *DB = sub () {1} }  # debugging output  0=off 1=on 2=verbose

and a bunch of stuff like

  print "DB:  REDIRECT!  new url is [$redirected_url]\n" if DB;

or

  print "DB: [$u] = [$robots_txt]\n" if (DB > 1);

or

  print "DB: now processing [$file]\n" if DB;

which when I have it turned on lets me track what's what pretty easily.

That's a general thing.  As for how to exit when Wrong Things Happen,
that varies with what your code is, but typical methods are

  die XML::Checker::error_string($code, @_) if ($code < 200);

  open( SENDMAIL, "| $SENDMAIL" ) or die "No sendmail?! $!";

  &err_bad_multi_file( $@ ) if ( $@ );  # do some cleanup and die

  flock( SUMMARY, $LOCK_EX) or exeunt( __LINE__, "Can't flock SUMMARY: $!" );


Hope these ideas help.

Walter