Why doesn't sed respect the simple regex?

Question

My text:mmhmmh here_is_you 05451ab8 888
My regex: mmhmmh \w* ([ab0-9]*) \d*
My sed command: echo "mmhmmh here_is_you 05451ab8 888" | sed -n 's/mmhmmh \w* \([ab0-9]*\) \d*/\1/p'
Result: 05451ab8888 instead of 05451ab8

Why doesn't sed respect my regex? I checked and my regex should correctly select the expected result.

Possible duplicate of [Why doesn't \`\d\` work in regular expressions in sed?](https://stackoverflow.com/questions/14671293/why-doesnt-d-work-in-regular-expressions-in-sed) and [Can't match regex with sed](https://stackoverflow.com/q/39103215/3776858) — Cyrus, Aug 16 '19 at 05:19
See also https://stackoverflow.com/questions/18514135/bash-regular-expression-cant-seem-to-match-s-s-etc — tripleee, Aug 16 '19 at 05:28

Jotne · Accepted Answer · 2019-08-16T05:46:59.910

-1

As Cyrus points out with the comment link, \d does gives problems, use [0-9]

echo "mmhmmh here_is_you 05451ab8 888" | sed -n 's/mmhmmh [a-zA-Z0-9_]* \([ab0-9]*\) [0-9]*/\1/p'
05451ab8

Or [[:digit:]]

echo "mmhmmh here_is_you 05451ab8 888" | sed -n 's/mmhmmh [[:alnum:]_]* \([ab0-9]*\) [[:digit:]]*/\1/p'
05451ab8

And as trpleee points out, do not use \w either.

edited Aug 16 '19 at 05:46

answered Aug 16 '19 at 05:25

Jotne

You also need to fix `\w`. It might work in some `sed` variants but it is not portable. – tripleee Aug 16 '19 at 05:32
@tripleee updated. – Jotne Aug 16 '19 at 05:48

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