in reply to Re^2: problems using Expect.pm in foreach loop
in thread problems using Expect.pm in foreach loop

The reason I was doing that is because if the '/^\s*exit\s*$/i' matched, that means the isql code is an exit statement, which would cause the isql program to terminate, thus I would not want to expect another '\d+\>' prompt.

Taking the if statement out, makes the code work as expected, although I'm not sure why. Also, it does not seem to cause a problem when the exit statement is given. It doensn't hang expecting another prompt. The program just exits, but I really don't understand why.

Can someone help explain? What if I do want to only expect a prompt if the $line does not match '/^\s*exit\s*$/i' ?

Thanks for helping me get this code working and thanks in advance for helping me understand the behavior better.

-G
  • Comment on Re^3: problems using Expect.pm in foreach loop

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Re^4: problems using Expect.pm in foreach loop
by keszler (Priest) on Sep 11, 2011 at 04:59 UTC

    The postfix if (! $line=~m/^\s*exit\s*$/i) is not doing what you expected.

    #!/usr/bin/env perl
use strict;
my $line = 'not an exit statment';
print "line matched ! =~\n"      if (! $line =~ m/^\s*exit\s*$/i   );
print "line matched !(=~)\n"     if (! ($line =~ m/^\s*exit\s*$/i) );
print "line matched not =~ \n"   if (not $line =~ m/^\s*exit\s*$/i );
print "line matched if !~\n"     if ( $line !~ m/^\s*exit\s*$/i );
print "line matched unless =~\n" unless ($line =~ m/^\s*exit\s*$/i);
__END__
line matched !(=~)
line matched not =~
line matched if !~
line matched unless =~

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    The ! operator has a much higher precedence than the not operator does. Using parentheses with the ! applies it to the result of the match; not with its lower precedence does so by default.

    When $exp->send sends the exit command to isql, isql disconnects and Expect.pm notices and handles that. If you are writing a production-quality program - especially one that will run automatically - you'll want to code your own checks for errors, disconnects, etc. OTOH, if this is for your own use only, run manually to simply automate a task, then you can usually get away with letting the Expect module handle anomalies. (I assume you're backing up whatever DB objects are being modified prior to letting a program make changes...)


    Update: added != and unless tests as additional examples
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      just wanted to thank you for your exellent replies. Very helpful! THANK YOU!
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      That was truly an excellent response keszler. Thank you for that! I understand now what was happening with my attempt to match "exit".

      Also, thank you for the added info about error checking the isql exit.

      Thanks everyone for your posts.
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