CODEWITHSUNDEEP
linuxgrep
user3750474
user3750474

Reputation: 259

Multiple grep search

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?

Upvotes: 2

Views: 160

Answers (2)

Two-Bit Alchemist
Two-Bit Alchemist

Reputation: 18467

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

Upvotes: 3

Victor Sorokin
Victor Sorokin

Reputation: 11996

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

Upvotes: 1

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