find pattern

Shell Programming and Scripting
1

Pls help with this clue:

a goal is to find a pattern and then ...
a) if it is found: {print $0}
b) if not: {print "NOT EXIST"}

2

Use the man pages:

man grep
3

Sorry. I was not precize. I want to include this search into awk program.
I know how to do the search and how to use if statement into awk. But I cannot manage to join those two. Maybe silly, but ...

4

With AWK

 awk '{ if ( $0 ~ /PATTERN/ ) print $0 ;  else print "NOT FOUND" } ' file.txt

With SED

 sed -n  -e   '/PATTERN/!s/.*/NOT FOUND/gp' -e '/PATTERN/p'  file.txt
5 
awk '{print /pattern/?$0:"NOT EXIST"}' infile