How to search for multiple strings in a file

Question

I want to search for the occurrence of string1 OR string2 OR string3, etc. in a file, and print only those lines (to stdout or a file, either one). How can I easily do this in bash?

Answer 1

grep "string1\|string2\|string3" file_to_search_in

Answer 2

Also:

grep -e 'string1' -e 'string2' -e 'string3'

Answer 3

you can also use awk

awk '/string1|string2|string3/' file

With awk, you can also easily use AND logic if needed.

awk '/string1/ && /string2/ && /string3/' file

Answer 4

With Perl:

perl -lne 'print if /string1|string2|string3/;' file1 file2 *.fileext

With Bash one liner:

while read line; do if [[ $line =~ string1|string2 ]]; then echo $line; fi; done < file

With Bash script:

#!/bin/bash

while read line
do
    if [[ $line =~ string1|string2|string3 ]]; then
       echo $line
    fi
done < file 

Note that the spaces around "[[ $line =~ string1|string2 ]]" are all relevant. ie these fail in Bash:

[[ $line=~string1|string2 ]] # will be alway true...
[[$line =~ string1|string2]] # syntax error

Answer 5

There are many acceptable answers already, but one other choice, especially if the number of strings you want to search is large, is to put those strings into a file, delimited by newlines and use

grep -f file_of_strings file_to_search