Syntax question...

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

Hello Monks, I am a complete perl newbie: I have inherited some ksh script with embedded perl and would like some syntax help. here is what I have recieved and added:

if [ "X${substitute}" = "Xy" -o "X${substitute}" = "XY" ]
then
    cat $inputfile |  perl -e 'while(<STDIN>)
    {
            if( length( $_ ) > 3 )
            {
                 @args=split(/\|/,$_);
        if( $args[1] eq '$service' && $args[3] eq '$bundle' )
        {
                    @args=split(/\|/,$_);
                    $args[4] =~ s/N/Y/;
                    print join("|",@args);
        }
                else
        {
                    print $_
        }
            }
            else
            {
            print $_
            }
    }' > $tmpfile
[download]

The gist of the code is to modify a line in a file by counting out args seperated by a |.

TIA,

tm

Comment on Syntax question... Download Code

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Re: Syntax question... by Fletch (Bishop) on Apr 17, 2002 at 16:24 UTC
And your question is . . . ? That obvious lack not withstanding: Useless use of `cat`; pass the filename to be grobbled as an argument Use `-p`, and possibly `-i` given the fact that it's outputting to a temporary file probably with the intention of replacing `$inputfile` with the munged version. See `perldoc perlrun`	[reply] [d/l] [select]
Re: Syntax question... by Juerd (Abbot) on Apr 17, 2002 at 16:22 UTC
And the question is...? We can't help you unless you specify a question :) Here is a rewrite, by the way: [untested] `perl -pe' if (length > 3) { my @args = split /\\|/; # I'm surprised the following line works in a # shell script, with the single quotes and all... if ($args[1] eq '$service' and $args[3] eq '$bundle') { $args[4] =~ s/N/Y/; $_ = join "\|", @args; } } ' $inputfile` [download] There, with proper indenting and an implicit loop and use of implicit handling of $_, it looks a lot better. If you add -i, the file itself will be changed, which may remove the need for a temporary file. - Yes, I reinvent wheels. - Spam: Visit eurotraQ.	[reply] [d/l]
Re: Syntax question... by jepri (Parson) on Apr 17, 2002 at 16:21 UTC
You don't seem to define `$service` or `$bundle` anywhere. If you defined them in a ksh script, or as environment variables, perl won't automatically pick them up. You will have to arrange for perl to get at them somehow. IIRC, `%ENV` holds environment variables, so that's probably the easiest way combined with shell scripts. ____________________ Jeremy I didn't believe in evil until I dated it.	[reply] [d/l] [select]
Re: Syntax question... by erikharrison (Deacon) on Apr 17, 2002 at 16:24 UTC
This seems to do what you want. A single advisement - `$service` and `$bundle` both look like Perl scalars - these scalars will not interpolate into a single quoted string, as you have them. As these (possible) variables are also not defined in your script, then I think that the single quotes are probably intentional - but you might want to make sure. Also, I don't know a thing about ksh, but I am pretty sure that with this ratio of embedded Perl to ksh, then this might profitably be rewritten as a pure Perl program, also helping you learn the language. Cheers, Erik	[reply] [d/l] [select]