grep exact match code example

Example 1: grep not match

Just filter your output with:
grep -v "excluded_pattern"
Example to get all not txt files in current directory.
ls | grep -v .txt

Example 2: grep third match

#Combine grep and tail for grepping until second match and filtering 
#last with tail command
grep -m2 "two" in-file.txt | tail -n1

Example 3: grep first match

Just combine grep with head command for filtering  only the first match as:
grep "match" | head -n 1   #Change 1 to not only match first but further matches

Example 4: grep or match

$ grep "PATTERN1\|PATTERN2" FILE
$ grep -E "PATTERN1|PATTERN2" FILE
$ grep -e PATTERN1 -e PATTERN2 FILE
$ egrep "PATTERN1|PATTERN2" FILE