Linux Common Command-egrep and extended regular expressions

Extending regular Expressions

Extended Regular Expression command: Egrep

Regular expressions are not supported but fast: fgrep

Character Matching:

.:

[]:

[^]:

Number of matches:

*:

?:

+: Match the characters in front of it at least once

{m}: Exact match

{M,n} no backslash required:

Location anchoring:

^:

$:

\< or \b:

\> or \b:

Group:

(): Group

\1,\2,\3,......

Or

|: or (A|B)

Cases:

C|cat=c or Cat

(c|c) At=cat or cat

Lazy Qualifier

*? Repeat any number of times, but repeat as little as possible

+? Repeat 1 or more times, but repeat as little as possible

?? Repeat 0 or 1 times, but repeat as little as possible

{n,m}? Repeat N to M times, but repeat as little as possible

{N,}? Repeat more than n times, but repeat as little as possible

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Linux Common Command-egrep and extended regular expressions