[regex] grep's at sign caught as whitespace

I ran into a problem while trying to grep a file that contains the following:

@abc abc  abc  @abc@  @abc@   @abc@ acb abc@ assd dsasd abc@  

I tried various grep commands, but there was a problem and abc@ or @abc were caught as whitespace in my regexps. I want the output, in general, to simulate the following script's output (only the "Good" ones):

for res in $(grep -F 'abc' test.txt); do if [[ ! $res == *@* ]]; then echo $res is good; else echo $res is bad; fi; done

This question is related to regex linux ubuntu grep

The answer is


No -P needed; -E is sufficient:

grep -E '(^|\s)abc(\s|$)' 

or even without -E:

grep '\(^\|\s\)abc\(\s\|$\)' 

After some time with Google I asked on the ask ubuntu chat room.

A user there was king enough to help me find the solution I was looking for and i wanted to share so that any following suers running into this may find it:

grep -P "(^|\s)abc(\s|$)" gives the result I was looking for. -P is an experimental implementation of perl regexps.

grepping for abc and then using filters like grep -v '@abc' (this is far from perfect...) should also work, but my patch does something similar.


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