CODEWITHSUNDEEP
regexshellunixsedgrep
Roy
Roy

Reputation: 69

regex working in egrep, but not in sed

I'm trying to identify the country abbreviations in a text.

egrep "^[A-Z]{2}$" file

seems to work. But when I'm trying the regex on sed, it's not working. This is what I'm using

sed 's/^[A-Z]{2}$/someCountry/' file

What am I doing wrong?

Upvotes: 1

Views: 135

Answers (2)

Thomas Dickey
Thomas Dickey

Reputation: 54475

POSIX sed uses BREs (basic regular expressions). In those, you can use the equivalent of {2}, but you must escape the braces. egrep supports EREs (extended regular expressions). As a side-effect of extending the BREs, the rules for escaping are different (to make the resulting expressions simpler to write).

For reference:

When a BRE matching a single character, a subexpression, or a back-reference is followed by an interval expression of the format "\{m\}", "\{m,\}", or "\{m,n\}", together with that interval expression it shall match what repeated consecutive occurrences of the BRE would match. The values of m and n are decimal integers in the range 0 <= m<= n<= {RE_DUP_MAX}, where m specifies the exact or minimum number of occurrences and n specifies the maximum number of occurrences. The expression "\{m\}" shall match exactly m occurrences of the preceding BRE, "\{m,\}" shall match at least m occurrences, and "\{m,n\}" shall match any number of occurrences between m and n, inclusive.

Upvotes: 2

Alex Hall
Alex Hall

Reputation: 36013

man sed and search for "extended". egrep is grep with a flag (-e on some platforms) for 'extended' regexes, and sed has a similar flag. Otherwise the syntax is different and you have to use \ a lot more.

Upvotes: 1

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