kluther has asked for the wisdom of the Perl Monks concerning the following question:

Hello all, I've an existing shell-script, but I would like to rewrite it in Perl. I'm new to Perl and now I stumble on something. In my shell-script I have the following line: 
if [ a`/usr/well561/bin/newlogfile 1` = aY ]; then
echo "true"
else
echo "false"
fi

[download]
when I do this in perl like this: 
if (`/usr/well561/bin/well.newlogfile 1` eq Y) {
print "true";
}
else {
print "false";
}

[download]
I get an error about using Bareword "Y" in strict mode, when I take the strict mode out I don't get the right result. How should I rewrite the above in Perl. I've tried several things but they don't work, mostly an error on Bareword "Y". Advise please Thanx Kluther

Replies are listed 'Best First'.
Re: shellscript to Perl
by LanX (Saint) on Mar 15, 2012 at 12:24 UTC
    Enclose the Y into quotes 'Y', to transform a bareword into a string-literal.

    Cheers Rolf

    PS: please enclose your code in <code>...</code> tags.

[reply]
[d/l]
[select]
Re: shellscript to Perl
by eyepopslikeamosquito (Archbishop) on Mar 15, 2012 at 21:47 UTC

    Also, note that shell backticks remove the trailing newline, while Perl backticks preserve it.

    Given you are just starting with Perl, it is a good idea to sprinkle print statements and error checks in your script to help you understand what is going on. To get you started, try this: 

    use strict;
use warnings;
my $cmd = '/usr/well561/bin/well.newlogfile';
-f $cmd or die "error: '$cmd' not found";
-x $cmd or die "error: '$cmd' not executable";
my $out = `$cmd 1`;
my $rc = $? >> 8;
print "command exit code is $rc\n";
$rc == 0 or warn "warning: command returned $rc\n";
chomp $out;    # remove trailing new line from command output
print "command output:$out:\n";
if ($out eq 'Y')
{
   print "command returned Y\n";
}

    [download]
    Study the script above, referring to the Perl documentation, and you should be on your way to rewriting your old shell scripts in Perl. As for learning Perl, take a look at learn.perl.org and Perl Tutorial Hub. Good luck!

[reply]
[d/l]
Re: shellscript to Perl
by Anonymous Monk on Mar 15, 2012 at 12:27 UTC
[reply]
Re: shellscript to Perl
by osbosb (Monk) on Mar 15, 2012 at 12:26 UTC
    http://perldoc.perl.org/functions/system.html

    http://perldoc.perl.org/perlop.html#Quote-Like-Operators <-- read about qx.

[reply]
Re: shellscript to Perl
by muppetjones (Novice) on Mar 16, 2012 at 19:11 UTC

    Perhaps I'm misinterpreting your post, but is "Y" a variable or a character?
    The compiler is complaining because it doesn't know how to handle 'Y' -- you need to either use it as a variable, i.e., $Y or surround it by quotes, i.e., 'Y'.

    As a side note, it is generally slightly faster to use single quotes rather than interpolating a variable or special character, e.g,
    'Hello world.' vs. "Hello world",
    'The number is '.$num vs "The number is $num", or
    'Hello world.'."\n" vs "Hello world\n".

[reply]
[d/l]
[select]

Back to Seekers of Perl Wisdom