1. An Overview of Grep and Regular Expression
By: Shuwei Chen

2. What is Grep? Text search utility Written for Unix
Global Regular Expression Print

3. Grep Format grep options pattern inputFileNames
grep -i apple fruitlist.txt

4. Basic Grep Usage Text file fruitlist.txt grep apple fruitlist.txt
banana
pineapple
Apples
grep apple fruitlist.txt
Did not return Apples, case sensitive.

5. Common Grep Options -i -v -w -x Ignores case distinctions
Lines that do NOT contain pattern -w
Searches for pattern as a word -x
Said pattern must match entire line

6. Common RegEx “.” – Any single character “?” - Zero or one times
p.g -> pig, pog, pag, peg
“?” - Zero or one times
las?t -> last, lat
“*” – Zero or more times
las*t -> last, lat, lasst, lassst
“+” – One or more times
las+t -> last, lasst, lassst

7. Common RegEx Cont. “{n}” – Exactly n times “{n,}” – n or more times
a{5} -> aaaaa
“{n,}” – n or more times
a{2} -> aa, aaa, aaaa
“{,m}” – At most m times
a{,3} -> a, aa, aaa
“{n,m}” – n to m times
a{2, 3} -> aa, aaa

8. Common Regex Cont. “[a,b,c]” – Any single character in bracket
b[o,b,q,w,e] -> bo, bb, bq, bw, be
“[a-z]” – Dash is a range indicator
b[a-d] -> ba, bb, bc, bd
“[^a,b,c]” - Any single character not in bracket
b[^a-y] -> bz

9. Other RegEx “[:digit:]” – Any digits
“[:alpha:]” – Any alphabetic characters
“[:upper:]” – Any uppercase characters
“[:lower:]” – Any lowercase characters
“^” – At the beginning of the line
“$” – At the end of the line
Other more complicated RegEx patterns

10. Sources http://www.gnu.org/software/grep/manual/grep.pdf