CODEWITHSUNDEEP
regexperl
djswartz
djswartz

Reputation: 177

Perl regex replace?

Why does this work:

$my_str=~s/://g;

But this does not:

$my_str=~s/:://g;

I have a string that looks something like this: ::this:is:my:string and I need to remove the :: but not touch the :.

Upvotes: 4

Views: 35486

Answers (3)

Ken Simon
Ken Simon

Reputation: 1544

Works fine for me:

$ echo "::this:is:my:string" | perl -ne "s/:://g; print;"
this:is:my:string

Upvotes: 13

ikegami
ikegami

Reputation: 385565

There are two things I can think of that would cause $my_str =~ s/:://g; fail:

  1. $my_str doesn't contains what you say it contains.
  2. pos($my_str) is set.

To make sure $my_str contains what you think it does, you could use Data::Dumper, but make sure to do $Data::Dumper::Useqq = 1; before using Dumper.

But first, make sure you aren't doing something like

if ($my_str =~ /.../g) {
   ...
   $my_str =~ s/:://g;
   ...
}

if ($my_str =~ /.../g) is a common mistake, and it could cause this problem. (I don't know why since it doesn't even make sense conceptually.) If so, get rid of the g in the if condition.

Upvotes: 3

Kevin
Kevin

Reputation: 56049

Are you sure you don't have any typos in your code? And that this substitution is in fact the problem? The following program worked for me:

my $var = '::a:b:c::';
print "$var\n";
$var =~ s/:://g;
print "$var\n";

Output:

$ perl test.pl
::a:b:c::
a:b:c
$

Edit to add a couple suggestions:

  1. Print the variable immediately before and after the substitution.
  2. No immediately the problem at hand, but if you only need to remove the :: at the beginning of the string, you may want to add a ^ to the regex to indicate that.

Upvotes: 7

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