Linux – `grep`-like utility to match strings instead of lines

greplinuxregex

I'm using grep to extract lines that match a regular expression. How to get only the matches and not the whole line?

You can supply grep the -o option. Like such:

grep -o pattern file

(Hint: The mnemonic I use for this is: omit everything except match)

Sure. That's pretty easy:

find . | grep -P '^\./[^/]*$'

... where obviously the 'find' command I'm using just to illustrate what you described. The regex works as follows:

^ and $ are anchors specifying (respectively) the beginning & end of the line. All content must be between those two characters
\./ is a literal period followed by a literal forward-slash
[^] is a character-class that disallows anything after the ^ and before the ]
The * after [^/] says to allow zero or more occurrences of that character class

You could also do it like this:

dosomething | grep -P '^[^/]*/[^/]*$'

This will allow only a single / on the line, in any position on the line (even first or last character).

try this:

grep -o -E "your expression" file |wc -l

well, -E is just an example, it could be -P, -F etc. point is -o

test:

kent$  echo "abc xxx yyy"|grep -cP "[a-z]{3}"      
1

kent$  echo "abc xxx yyy"|grep -oP "[a-z]{3}"|wc -l
3