Dynamic replacing with perl

Question

I want to programmatically replace little placeholder with static content like the user name or working path.

Is there a possibility in bash that I can dynamically execute my perl replacement state like:

GROUPNAME="$(id -g -n $USER)"
perl -pi -e 's/\(PLACEHOLDER\)/' + "$GROUPNAME" + '/g' filepath/file

it would be the enormously good if I could also adapt this dynamical behaviour for the placeholder. But first things first. How do I concatenate these strings?

Not sure if that's a good match, because it's about variables. — Karoly Horvath, Nov 04 '15 at 13:51

score 6 · Accepted Answer · edited Nov 04 '15 at 14:13

6

Remove " + " (spaces and plus). Bash does automatic concatenation for adjacent strings.

echo 'hi!'t"here"  # hi!there

Generating Perl code in this way is only safe because the output of id -g -n $USER won't contain \, $, @ or /.

edited Nov 04 '15 at 14:13

ikegami

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answered Nov 04 '15 at 13:47

Karoly Horvath

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@ikegami: This use case is safe. Perhaps use `sed` for clarity. – Karoly Horvath Nov 04 '15 at 14:09
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It's coming from a trusted input (`id`). – Karoly Horvath Nov 04 '15 at 14:11

ikegami · Answer 2 · 2015-11-04T15:10:17.970

You were going for

GROUPNAME="$(id -g -n $USER)"
perl -i -pe's/\(PLACEHOLDER\)/'"$GROUPNAME"'/g' filepath/file

But there's no reason to generate Perl code. That is very error prone. Instead, use one of the following:

export GROUPNAME="$(id -g -n $USER)"
perl -i -pe's/\(PLACEHOLDER\)/$ENV{GROUPNAME}/g' filepath/file

or

GROUPNAME="$(id -g -n $USER)" perl -i -pe's/\(PLACEHOLDER\)/$ENV{GROUPNAME}/g' filepath/file

Dynamic replacing with perl

2 Answers2