Replace text between 2 strings (inclusive)

Question

Is there a perl one-liner that could replace some text between 2 strings (inclusive)? For example in the text below I need to replace everything between 'rrpv_bits = 2' and 'options.cacheline_size' with 'num_sets = 512' everywhere in the text where these 2 tag strings are found. So the original text would look like the desired one.

Original:

    repl = ReplacementPolicy(rrpv_bits = 2,
                             ins = 2,
                             num_sets = l2_cache.size.getValue() /
                             options.l2_assoc / options.cacheline_size,
                             assoc = options.l2_assoc)

Desired:

    repl = ReplacementPolicy(num_sets = 512,
                             assoc = options.l2_assoc)

If a perl one-liner can't do that then is there anything else (Linux, one-liner) that can?

Thank you

Miller · Accepted Answer · 2014-06-24 00:56:08Z

1

If they always exist together, a perl one-liner:

perl -0777 -pe 's/rrpv_bits = 2.*?options\.cacheline_size/num_sets = 512/gs' file.txt > newfile.txt

However, this approach is likely too greedy. What would happen if the first boundary matches but not the second in a ReplacePolicy call? Then the regex will just eat up all the lines until it finds a second ReplacePolicy that does contain the end condition.

Therefore, to protect against this, we can limit the characters between boundary conditions to only allow balanced parenthesis. This would lock the matching to within the parameters of a ReplacePolicy:

perl -0777 -pe 's/rrpv_bits = 2((?:[^()]*|\((?1)\))*)options\.cacheline_size/num_sets = 512/gs;' file.txt > newfile.txt

Explanation:

Switches:

-0777: Slurp the entire file
-p: Creates a while(<>){...; print} loop for each “line” in your input file.
-e: Tells perl to execute the code on command line.

edited Jun 24, 2014 at 0:56

answered Jun 24, 2014 at 0:33

Miller

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1 Comment

Dimon Over a year ago

Yes they do. amazing. Thank you so much.

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