I was trying a multiple grep search, but for some reason it wasn't working:
Input:
What time is it in India
Time in Israel
Dogs are awesome
I want chocolate cake
Desire Output:
What time is it in India
chocolate cake
I used the command:
grep "(What time is it)|(chocolate cake)" inputfile.txt
However I got the an empty output instead. Would you know why this is going wrong?
You have to escape the pipe (|) because it is a special character.
grep "what time is it\|chocolate cake" inputfile.txt
The parens in your regex are superfluous and can be left off. If you leave them, they must also be escaped:
grep "\(what time is it\)\|\(chocolate cake\)" inputfile.txt
Use egrep instead of grep. grep does not understand regexp you used:
$ egrep "(what time is it)|(chocolate cake)" input.txt
what time is it in India
i want chocolate cake
More precisely, man grep on modern Unix-like system tells:
In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, +, {, \|, (, and ).
So, following will work with the same result:
grep "\(what time is it\)\|\(chocolate cake\)" input.txt
