CODEWITHSUNDEEP
regexbashsed
maro
maro

Reputation: 503

How to remove last characters from a string in bash using sed?

I would like to change all occurrences like "waaa", "wwwaaaaa", "wa" by trimming all the "a" in the end.

waaa > w
wwa > ww
waaaaa > w

I know how to find these strings in a text using regular expressions:

grep -nE "wa+" file.txt

I also know how to change one string in a bash script

#!/bin/bash
s1="wwwwaaaaaaaa"
s2=${s1%w*}
echo "$s1 --> $s2"

(modified script from https://stackoverflow.com/a/27658717/5219155)

But I would like to use someting like

sed -E 's/wa+/ZZZ/' file.txt

where ZZZ is something that I need here.

sed -E 's/wa+/${$1%w*}/' file.txt

doesn't work.

Sample input:

Lorem ipsum wa waaaaaaa saaa dolor sit amet,
consectetur aw awwwwaaaa adipiscing elit

Desirable output:

Lorem ipsum w w saaa dolor sit amet,
consectetur aw awwww adipiscing elit

Upvotes: 0

Views: 493

Answers (2)

PesaThe
PesaThe

Reputation: 7519

sed 's/waa*\b/w/g' file

sed 's/waa*\>/w/g' file

or using extended regex:

sed -r 's/wa+\b/w/g' file

\b and \> are word boundaries. For more information, see this regex tutorial: Word Boundaries.

Upvotes: 5

glenn jackman
glenn jackman

Reputation: 247220

With bash, use extended pattern matching to remove all the "a" from the end of the string:

shopt -s extglob
for str in "waaa" "wwwaaaaa" "wa"; do
    new="${str%%+(a)}ZZZ"
    echo "$str => $new"
done

waaa => wZZZ
wwwaaaaa => wwwZZZ
wa => wZZZ

Upvotes: 0

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