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I have a lot of lines in my LIST file and want to list only lines whose name does not start by (or contains) "git".

So far I have :

cat LIST | grep ^[^g]

but I would like something like :

#not starting by "git"
cat LIST | grep ^[^(git)]
#not containing "git"
cat LIST | grep .*[^(git)].*

but it is not correct. What regex should I use ?

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up vote 6 down vote accepted

Using grep in this case with -P option, which Interprets the PATTERN as a Perl regular expression

grep -P '^(?:(?!git).)*$' LIST

Regular expression explanation:

^             the beginning of the string
 (?:          group, but do not capture (0 or more times)
   (?!        look ahead to see if there is not:
     git      'git'
   )          end of look-ahead
   .          any character except \n
 )*           end of grouping
$             before an optional \n, and the end of the string

Using the find command

find . \! -iname "git*"
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1  
Not sure how/if the expression would be optimzed internally, but I wouldn't use the quantifier + on the outer group. Considering it won't capture its match I'd simply remove it alltogether for a more simple/readable expression. – Mario Oct 13 '13 at 9:50
    
This expression will match anything from start to end of a line that does not start with git – hwnd Oct 13 '13 at 14:27
    
Your first command is what I am looking for :) However I do not understand what (?!git) does ? – Vulpo Oct 13 '13 at 16:28
    
It is a negative look ahead assertion, see updated edit. – hwnd Oct 13 '13 at 16:33

If you want to simply list all lines that don't contain git try this

 cat LIST | grep -v git
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In that specific case, it does work. Thanks. But I would have preferred the use of regular expressions since it can be used in much more cases (for exemple a perl script parsing a user input). – Vulpo Oct 8 '13 at 11:15
    
Maybe this post on SO has what you need. – dinesh Oct 8 '13 at 16:55
    
Almost. I try to match what does NOT contain the string. Without using "-v" option from grep if possible :) – Vulpo Oct 11 '13 at 9:33

Since the OP is looking for a general regex and not specially for grep, this is the general regex for lines not starting with "git".

^(?!git).*

Breakdown:

^ beginning of line

(?!git) not followed by 'git'

.* followed by 0 or more characters

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