Using Perl instead of awk!

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

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Re: Using Perl instead of awk! by eyepopslikeamosquito (Archbishop) on Sep 30, 2014 at 19:25 UTC
Something like this should get you started: `use strict; use warnings; my $fname = '/dir/file'; open my $fh, '<', $fname or die "error: open '$fname': $!"; while (<$fh>) { next unless /something/; my @flds = split; print "$flds[2]\n"; }` [download] See open and split.	[reply] [d/l]
Re: Using Perl instead of awk! by choroba (Cardinal) on Sep 30, 2014 at 19:33 UTC
Backquotes interpolate variables, and $3 is a special variable in Perl. So, Perl interpolates it (but it's probably empty, do you use warnings?) before awk can see it. You can prevent interpolation by backslashing the dollar sign. But... Why would you call awk from Perl? You can get the same result without shelling out. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply]
Re: Using Perl instead of awk! by runrig (Abbot) on Sep 30, 2014 at 21:04 UTC
The result is more verbose than it needs to be, but the last part is fairly straightforward: $ a2p <<'EOT' > /something/ { print $3 } > EOT #!/usr/local/bin/perl eval 'exec /appl/toolbox/perl5.8.8/bin/perl -S $0 ${1+"$@"}' if $running_under_some_shell; # this emulates #! processing on NIH machines. # (remove #! line above if indigestible) eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift; # process any FOO=bar switches $, = ' '; # set output field separator $\ = "\n"; # set output record separator while (<>) { ($Fld1,$Fld2,$Fld3) = split(' ', $_, -1); if (/something/) { print $Fld3; } } [download] Updated/fixed...single quoted 'EOT'	[reply] [d/l]
Re: Using Perl instead of awk! by Tux (Canon) on Oct 01, 2014 at 06:31 UTC
When you do know awk, and want to see/learn how the same thing is done in perl, you can use the awk-to-perl tool `a2p` that shipped with perl. The generated perl code is probably (very) inefficient, but at least shows you how the conversion could be done: `$ echo '/something/ { print $3 }' \| a2p #!/pro/bin/perl eval 'exec /pro/bin/perl -S $0 ${1+"$@"}' if $running_under_some_shell; # this emulates #! processing on NIH machines. # (remove #! line above if indigestible) eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift; # process any FOO=bar switches $, = ' '; # set output field separator $\ = "\n"; # set output record separator while (<>) { ($Fld1,$Fld2,$Fld3) = split(' ', $_, -1); if (/something/) { print $Fld3; } }` [download] Enjoy, Have FUN! H.Merijn	[reply] [d/l] [select]
Re: Using Perl instead of awk! by karlgoethebier (Abbot) on Sep 30, 2014 at 19:24 UTC
Not sure if i got it... but turn on auto split `karls-mac-mini:monks karl$ echo foo bar nose cuke > file karls-mac-mini:monks karl$ echo foo bar nose cuke >> file karls-mac-mini:monks karl$ cat file foo bar nose cuke foo bar nose cuke # bullshit! perl -lnae 'print $F[3];' file perl -lne '/(cuke)/;print $1' file cuke cuke karls-mac-mini:monks karl$` [download] Update: Shit! Did you mean this? See perlrun. Regards, Karl «The Crux of the Biscuit is the Apostrophe»	[reply] [d/l]
Re: Using Perl instead of awk! by codiac (Beadle) on Oct 01, 2014 at 01:56 UTC
For your code to work you need to escape the '$' awk is using: my $pSWP = `awk '/something/ { print \$3 }' /dir/file`; [download] But like others said, why use awk when you can do it in perl :)	[reply] [d/l]