[OneLiner] What am I doing wrong in my regex?

[three18ti]

Hello Monks

I had to bump the version in a number of files; as it was too many to do by hand I thought I could handle it in a oneliner.

Spoiler alert: I did get it worked out with a oneliner (at the end), but I'm flummoxed to no end as to why my first attempt was not working. Can anyone give me any clues to what I was doing wrong?

Here are my wrong initial attempts (and their output), the first one is probably the most puzzling, if $version is undef, where did "version '1.2.36'" come from?!?:

printf "foo\nversion   '1.2.36'\nbaz\n" | perl -MData::Dumper -pi -e "
+next unless /version/; ($version) = /version\s+('1\.2\.36')/; print $
+version"

    foo
    version   '1.2.36'
    version   '1.2.36'
    baz

printf "foo\nversion   '1.2.36'\nbaz\n" | perl -MData::Dumper -pi -e "
+next unless /version/; ($version) = /version\s+('1\.2\.36')/; print D
+umper $version"
 
    foo
    version   '1.2.36'
    baz

printf "foo\nversion   '1.2.36'\nbaz\n" | perl -MData::Dumper -pi -e "
+next unless /version/; ($version) = /version\s+('1\.2\.36')/; print D
+umper \$version"

    foo
    $VAR1 = undef;
    version   '1.2.36'
    baz

printf "foo\nversion   '1.2.36'\nbaz\n" | perl -pi -e 'next unless /ve
+rsion/; ($version) = $_ =~ m{ version \s+ ''(1[.]2[.]36)'' }xms; prin
+t "version:" . $version . "\n"'

    foo
    version:
    version   '1.2.36'
    baz

Now of course, doing this in a script works:

$ cat wtf.pl
#!/usr/bin/perl
use 5.010;
use strict;
use warnings;

while (<>) {
  next unless /version/;
  my ($version) = /version \s+ '(\d+[.]\d+[.]\d+)'/msx;
  say $version;
}

$ printf "foo\nversion   '1.2.36'\nbaz\n" | perl wtf.pl
1.2.36

Epilogue: I did get it figured out, first of all, I only needed to change the last decimal point, so really I only needed to capture the last decimal point. I'm at a loss as to why this one works and my version was unable to match... (but I solved my problem so the issue is at least out of the way) (credit goes to my coworker)

printf "foo\nversion   '1.2.36'\nbaz\n" | perl -pi -e 'if ($_ =~ m/ver
+sion\s+.\d+[.]\d+[.](\d+)/) { my $v1 = quotemeta $1; my $v2 = $1 + 1;
+ $_ =~ s/$v1/$v2/ }'

    foo
    version   '1.2.37'
    baz

I appreciate any insight that may help me avoid obvious mistakes in the future (although I've driven myself up a wall trying to find any "obvious" mistakes...)

Thanks!

[Corion]

Most likely, shell quoting was tripping up your oneliners.

In most shells, double quotes interpolate variables. As you put your Perl oneliner in between double quotes, all the dollar signs were expanded to (empty) variables. You were unlucky in the sense that your program seems to have remained valid Perl even with all variables removed.

[perlfan]

> You were unlucky in the sense that your program seems to have remained valid Perl even with all variables removed.

Classic.