More Grep - Regular Expressions


 
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# 1  
More Grep - Regular Expressions

Hey all! I'm trying to search a file and return all instances of a word, let's say 'foo' in this case, as long as it's not a function name. For example:

1) int foo; //OK
2) //'this is totally fooed up' is also OK
3) int foo (int x, int y) //not ok to return

I've tried a lot of regular expressions but none of them work. Always is foo the function returned.

Here's what I think should work (but doesn't):

grep -E "foo[\s]*[\w]*[^(]" <filename

Any ideas as to why it doesn't work?
# 2  
Quote:
Originally Posted by Jombee
Here's what I think should work (but doesn't):

grep -E "foo[\s]*[\w]*[^(]" <filename

Any ideas as to why it doesn't work?
Can you try giving the same command without the '^' sign. That is supposed to match the start of the line.
# 3  
If I take out the ^ then grep matches nothing.

I'm not sure what you mean by it matches the beginning of a line...I thought that the ^ means not.

So basically, what I'm trying to express in a regular way is:

Return to me all the lines that have the string "foo" in them except when there is any amount of whitespace following the word "foo" that is then followed by a "(".

So, what's the deal?
# 4  
Code:
grep -E 'foo[^(]+$' filename

# 5  
Wow, that totally worked!

grep -E 'foo[^(]+$' index2.html

Can we go into this a little bit deeper?

-E: match using extended regular expressions.

[^(]: This is confusing me a little bit. Does this mean, "I don't care what comes after the string, as long as it's not a paranthesis?

+: This will happen one or more times

$: end of line?

Thank you so much, guys, for your help!
# 6  
Lets beak the pattern down: 'foo[^(]+$'

'foo' matches the string 'foo' anywhere in the line

'[^(]' matches any character except for a normal open braket '('

'+' means match 1 or more of the preceeding character class,in this case '[^(]'

'$' matches the end of the line

So verbosely, the pattern matches: the string 'foo' anywhere in the line followed by one or more characters to the end of the line as long as none of these characters is a '('.

The only case where this would not match a line you would probably want it to match is the case where the string 'foo' was at the end of a line.
# 7  
If you may have "foo" at the end of the line and still catch it you can use two regexps with the "-e" option:

grep -e "x" -e "y"

will find every "x" and "y".

hence:

grep -e "foo[^(][^(]*$" -e "foo$"

bakunin
 

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