CODEWITHSUNDEEP
regexbashsedgrep
brillout
brillout

Reputation: 7444

Same regex evaluated differently with sed than with grep

Consider following commands

~ echo "f(ew)" > t
~ egrep "f\([^\)]*\)" t
f(yo)

as expected egrep matches the whole line.

But for the following commands the regex doesn't catch the last parenthese

~ echo "f(ew)" > t
~ sed -i "s/f\([^\)]*\)/yo/" t
~ cat t
yo)

why isn't the last parenthese catched?

Upvotes: 3

Views: 69

Answers (2)

jaybee
jaybee

Reputation: 955

Escaping a parenthesis (== normal round brace) within the pattern in sed is part of the special mechanism we use to name the matched string in the substitution string by using \1, \2, etc.

So in your case you don't want sed to interpret your parenthesis as these special characters, but just leave them depict the character they are :) So:

sed -i 's/f([^)]*)/yo/' t

This is the solution brought by konsolebox, but @konsolebox: this is not "quoting/unquoting" that we are talking about, but "escaping" (the characters '(' and ')').

Upvotes: 1

konsolebox
konsolebox

Reputation: 75458

Don't quote it:

sed -i "s/f([^)]*)/yo/" t

Or perhaps use -E/-r:

sed -E -i "s/f\([^)]*\)/yo/" t
sed -r -i "s/f\([^)]*\)/yo/" t

-E or -r makes it interpret the pattern like egrep:

-r, --regexp-extended
       use extended regular expressions in the script.

Upvotes: 2

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