REGEX pattern to increment a counter on replacements - ruby

Question

In a replacement pattern, is there any way to print the NUMBER of the replacement as in a counter?
I have a series of code blocks I need to process in an HTML file, but in each replaced block I need to increment the counter by 1.
So
<p class-"foo">Some text</p>
<p class-"foo">Other text</p>
needs to be
<p id="1">Some text</p>
<p id="2">Other text</p>
I have many lines, I would love to avoid manually entering those numbers. How can i do this, the simplest way?

Answer 1

In Perl:
my $html = <<END;
<p class="foo">Some text</p>
<p class="foo">Other text</p>
END
my $n = 0;
$html =~ s/<p class="toc0">/'<p class="foo" id="'.++$n.'">'/eg;
print $html;
OUTPUT
<p id="1">Some text</p>
<p id="2">Other text</p>
For a command-line version to read from a file
perl -pe 's/<p class="toc0">/q(<p class="foo" id=").++$n.q(">)/eg' myfile.html

Answer 2

You can write:
perl -pe 's/<p class-"foo">/"<p id=\"" . (++$count) . "\">"/eg'
using the /e flag to treat the replacement as an expression rather than a string.

Answer 3

use awk
{ cat -<<EOS
<p class-"foo">Some text</p>
<p class-"foo">Other text</p>
EOS
} | awk '/<p class/{sub(/class-".*"/, "id=\""++i "\"");print}'
output
<p id-1>Some text</p>
<p id-2>Other text</p>
I hope this helps.

Answer 4

perl -pwe 's/<p\s+\Kclass-"foo">/ $i++; qq(id="$i">) /e' yourfile
The \K is used to keep whatever comes before it, which is convenient in this case. Using a replacement that is evaluated and contains several (two) statements is also convenient, to avoid concatenating and complicating quoting. It is only the return value of the entire statement that is inserted, i.e. the last statement.
When you've tried it out and want to alter the files, you can simply add the -i option. I would recommend using backups, like so:
perl -i.bak -pwe '....etc'
(Backup in filename.ext.bak)

Answer 5

irb(main):001:0> s = %Q{<p class-"foo">Some text</p>\n<p class-"foo">Other text</p>}
irb(main):002:0> id=0; s.gsub(/class-"foo"/) { id+=1; %Q[id="#{id}"] }
=> "<p id=\"1\">Some text</p>\n<p id=\"2\">Other text</p>"