GREP

GREP stands for Global Regular Expression Printer.

$ grep options pattern filename(s)

Options:

-i      ignore case                                   -c         count lines

-v     inverse role                                   -l          file names only

-n     lines are numbered                        -f          patterns in a file

-e     multiple patterns                            -E         EREs

REGULAR EXPRESSIONS USING GREP

Basic Regular Expressions (BRE):

*                       Zero or more occurrences of the prev. chr.

.                       A single Character

.*                      Any no. of characters or none

[abc]                 a or b or c

[a-z]                  any character between a to z

[1-3]                  any digit between 1 to 3

[^abc]               not a or not b or not c

REGULAR EXPRESSIONS USING GREP

Basic Regular Expressions (BRE):

[^a-zA-Z]           non-alphabetic character

abc                   exact character sequence abc                           

^abc                 abc not at the beginning of the line

abc$                 abc not at the end of the line

^abc$               abc as the only word in line

^$                     lines containing nothing

\                       nullify the meaning of meta characters

REGULAR EXPRESSIONS USING GREP

Extended Regular Expressions (ERE):

ab+c     a followed by one or more b’s followed by c

ab?c     a followed by optional b followed by c   abc or ac

a|b        either a or b

(a|b)c    either ac or bc

REGULAR EXPRESSIONS USING GREP

Interval Regular Expressions (IRE):

ab {2,4}c           a followed by 2,3,4 b’s followed by c

ab{2,}c a followed by at least  2b’s followed by c

ab{2}c               a with 2b’s and c

Ex:

grep –i  ‘abc’ emp.lst emp.lst1