SHELL

grep and

# EXAMPLE: displays any lines that contain either "include this string" or "this works too" 
egrep "include this string|this works too" *

# SYNTAX:
# egrep "<pattern-1>|<pattern-2>" *

# egrep is combined with the "|" character (pipeline: normally the shift alternative to the "" on the keyboard)

grep and

grep -E 'pattern1.*pattern2' filename
grep -E 'pattern1.*pattern2|pattern2.*pattern1' filename