CODEWITHSUNDEEP
macossed
sakhunzai
sakhunzai

Reputation: 14500

Mac OS X sed regexp

I am trying to do simple find replace digit while adding a value but failing to do so under Mac OS X, e.g.

echo "abc top: 234px" |sed -E 's/top:[[:space:]]*([0-9]+)/echo $(echo "\1+16"|bc)/g'

which should output: "abc top: 250px"

Instead it outputs: abc echo $(echo "234+16"|bc)px

Upvotes: 1

Views: 493

Answers (3)

Jotne
Jotne

Reputation: 41460

Here is an awk

echo "abc top: 234px" | awk '$NF=$NF+16"px"'
abc top: 250px

Some more robust with search for top:

echo "abc top: 234px" | awk '/top:/ {$NF=$NF+16"px";print}'
abc top: 250px

Here you do not need the format prefix px:

echo "abc top: 234px" | awk 'sub(/[0-9]+/,$NF+16)'
abc top: 250px

or 

echo "abc top: 234px" | awk '/top:/ {sub(/[0-9]+/,$NF+16);print}'
abc top: 250px

Upvotes: 2

Paul R
Paul R

Reputation: 213200

Difficult with sed, but here's a perl solution:

$ echo "abc top: 234px" | perl -pe 's/(\d+)/16 + $1/ge'
abc top: 250px

Upvotes: 1

tripleee
tripleee

Reputation: 189936

You cannot refer back to the back-reference using an external command -- when echo | bc is evaluated (once you fix the quoting so that they are evaluated at all in the first place), the sed script has not yet been parsed.

What you can do is switch to a tool which allows for arithmetic on captured values.

echo "abc top: 234px" |
perl -pe 's/(top:\s*)(\d+)/ sprintf("%s%i", $1, 16+$2)/ge'

Upvotes: 1

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