Exclude string from regular expression

Question

Is there a way to select only those lines from a text file which exclude a substring?For example, I have the file:

I have a /apple
I have a peach
I have a cucumber/strawberry
ABCDE
I have a apple/grape
XYZEF
POLSD

and i want to select the lines that start with 'I have a' but don't include the string 'apple'.So basically I want to select only:

I have a peach
I have a cucumber/strawberry

What application or programming language? If you're using `grep`, it has a `-v` option that prints the lines that don't match. — Barmar, Jan 10 '15 at 22:29

score 3 · Answer 1 · answered Jan 10 '15 at 22:47

3

Use a negative lookahead.

^I have a (?!.*\bapple\b).+

will match all "I have a" strings except ones that contain the entire word "apple". This will still match the phrase

I have a pineapple

because of the word boundaries around "apple".

answered Jan 10 '15 at 22:47

Jongware

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score 1 · Answer 2 · answered Jan 10 '15 at 22:41

1

Use a pipe:

grep '^I have a' file.txt | grep -v apple

answered Jan 10 '15 at 22:41

Danny Daglas

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score 0 · Answer 3 · answered Jan 10 '15 at 22:30

0

You should use the regular expression "starts with" with a multiline flag like this: "^I have a.*" /gm.

answered Jan 10 '15 at 22:30

Artak

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I think you may have misunderstood the question, as this doesn’t really help OP. – Konrad Rudolph Jan 10 '15 at 22:32

score 0 · Answer 4 · edited May 23 '17 at 11:57

For a pure regex solution, you can use something like:

^I have a (?!.*apple) - Note: You can also add \b word boundaries around the "apple", like Jongware suggested, if you don't want to match things like "pineapple".

However, a much easier way to do this (especially if the problem was a bit more complicated!) would be to combine a search for the first pattern, with a search excluding the second pattern.

With grep, as suggested by Danny Daglas, you can do grep '^I have a' file.txt | grep -v apple (where grep -v is an "inverse grep").

However, you wanted to do this inside a text editor, which is fair enough. The exact method obviously varies between text editors, but for example for Vim check out this excellent stackoverflow answer.

Exclude string from regular expression

4 Answers4