CODEWITHSUNDEEP
bashperlsed
gastone
gastone

Reputation: 23

Variable substitution in Perl with Perl special characters

I would like to substitute a substring that contains an @ character with Perl as in the following sed command:

substitution='[email protected]'
sed 's/[email protected]/'"${substitution}"'/g' <<< "The current e-mail address is [email protected]"

At present wherever I use Perl instead of sed or awk I first replace \ with \\, / with \/, $ with \$ and @ with \@; e.g.

substitution='[email protected]'
substitution="${substitution//\\/\\\\}"
substitution="${substitution//\//\\/}"
substitution="${substitution//$/\\$}"
substitution="${substitution//@/\\@}"
perl -pe 's/oldusername\@website.com/'"${substitution}"'/g' <<< "The current e-mail address is [email protected]"

I have read about using single quotation marks (as below based on sed/ perl with special characters (@)) but I was wondering if there is any other way to do this with forward slashes?

substitution='[email protected]'
perl -pe "s'[email protected]'"${substitution}"'g" <<< "The current e-mail address is [email protected]"

Also, are there special characters in Perl aside from $, @ and % (and why is there no need to escape %)?

Upvotes: 2

Views: 516

Answers (1)

choroba
choroba

Reputation: 241918

The cleanest way is to pass the values to Perl, as it can handle variables in substitution patterns and replacements correctly. Use single quotes so the shell's variable expansion doesn't interfere. You can use the -s option (explained in perlrun).

#!/bin/bash
[email protected]
[email protected]
perl -spe 's/\Q$pat/$sub/g' -- -pat="$pattern" -sub="$substitution" <<< "The current e-mail address is [email protected]"

or propagate the values to Perl via the environment.

[email protected]
[email protected]
pat=$pattern sub=$substitution perl -pe 's/\Q$ENV{pat}/$ENV{sub}/g' <<< "The current e-mail address is [email protected]"

Note that you need to assign the values before calling Perl or you need to export them in order to propagate them into the environment.

The \Q applies quotemeta to the pattern, i.e. it escapes all the special characters so that they are interpreted literally.

There's no need to backslash % as hashes aren't interpolated in double quotes or regexes.

Upvotes: 7

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