grep multiple code example
Example 1: grep in multiple files
grep -E 'fatal|error|critical|failure|warning|' *.log
Example 2: grep more than one word
Just use one of following forms with grep or egrep commands :)
grep "PATTERN1\|PATTERN2" FILE
grep -E "PATTERN1|PATTERN2" FILE
grep -e PATTERN1 -e PATTERN2 FILE
egrep "PATTERN1|PATTERN2" FILE