Question

I’m trying to change strings like this:

<a href='../Example/case23.html'><img src='Blablabla.jpg'

To this:

<a href='../Example/case23.html'><img src='<?php imgname('case23'); ?>'

And I’ve got this monster of a regular expression:

find . -type f | xargs perl -pi -e \
  's/<a href=\'(.\.\.\/Example\/)(case\d\d)(.\.html\'><img src=\')*\'/\1\2\3<\?php imgname\(\'\2\'); \?>\'/'

But it isn’t working. In fact, I think it’s a problem with Bash, which could probably be pointed out rather quickly.

r: line 4: syntax error near unexpected token `('
r: line 4: `  's/<a href=\'(.\.\.\/Example\/)(case\d\d)(.\.html\'><img src=\')*\'/\1\2\3<\?php imgname\(\'\2\'); \?>\'/''

But if you want to help me with the regular expression that’d be cool, too!

Answer 1

Teaching you how to fish:

s/…/…/

Use a separator other than / for the s operator because / already occurs in the expression.

s{…}{…}

Cut down on backslash quoting, prefer [.] over \. because we’ll shellquote later. Let’s keep backslashes only for the necessary or important parts, namely here the digits character class.

s{<a href='[.][.]/Example/case(\d\d)[.]html'>…

Capture only the variable part. No need to reassemble the string later if the most part is static.

s{<a href='[.][.]/Example/case(\d\d)[.]html'><img src='[^']*'}{<a href='../Example/case$1.html'><img src='<?php imgname('case$1'); ?>'}

Use $1 instead of \1 to denote backreferences. [^']* means everything until the next '.

To serve now as the argument for the Perl -e option, this program needs to be shellquoted. Employ the following helper program, you can also use an alias or shell function instead:

> cat `which shellquote`
#!/usr/bin/env perl
use String::ShellQuote qw(shell_quote); undef $/; print shell_quote <>

Run it and paste the program body, terminate input with Ctrl+d, you receive:

's{<a href='\''[.][.]/Example/case(\d\d)[.]html'\''><img src='\''[^'\'']*'\''}{<a href='\''../Example/case$1.html'\''><img src='\''<?php imgname('\''case$1'\''); ?>'\''}'

Put this together with shell pipeline.

find . -type f | xargs perl -pi -e 's{<a href='\''[.][.]/Example/case(\d\d)[.]html'\''><img src='\''[^'\'']*'\''}{<a href='\''../Example/case$1.html'\''><img src='\''<?php imgname('\''case$1'\''); ?>'\''}'