CODEWITHSUNDEEP
regexposixgrep
bukzor
bukzor

Reputation: 38492

grep: "^." doesn't match correctly with grep 2.5.1 and earlier

Can someone explain why this code doesn't work as expected? I would expect it only to match the first character, and it does with literal characters, but the wildcard (.) and characters classes behave strangely:

I use -o just to demonstrate exactly how things are matching, it doesn't change what matches at all.

$ echo foo | grep -o '^.'
f
o
o

Some more unexpected behavior:

$ echo foobarbazquux | grep -o '^[foarqux]'
f
o
o

$ echo foobarbazquux | grep -o '^.[^u]'
fo
ob
ar
ba
zq

Esentially the beginning-of-line matcher (^) is not behaving as expected in these cases. Is there any way to make it behave more normally?

Upvotes: 3

Views: 388

Answers (2)

ninjalj
ninjalj

Reputation: 43708

Found it:

Bug

Changelog of fix

Apparently fixed in 2.5.2. Found it via launchpad.

Upvotes: 5

Marc B
Marc B

Reputation: 360742

From my Ubuntu 10.04 box:

marc@panic:~$ echo foo | grep -o '^.'
f
marc@panic:~$ echo foobarbazquux | grep -o '^[foarqux]'
f
marc@panic:~$ echo foobarbazquux | grep -o '^.[^u]'
fo
marc@panic:~$ grep --version
GNU grep 2.5.4

There are a series of environment variables grep will look for to control its behavior/output, so check if any of those are set. Most likely you've got 'GREP_OPTIONS' set.

Upvotes: 0

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