-Regular expressions is used to perform powerful and efficient text processing
-It is simple like search editors and powerful text processing language
-This is powerful pattern language
-Matching performed based on the bit pattern used for the encoding the character not based graphic representation.
[ ] represent the character class in regex. Find some of the examples below
[PQR]-Matches either an P,Q or R character
Ex: P QQ RRR
[^PQR]-Matches any character except either an P,Q or R.
Ex: EVERYTHING
[P-Z]- Matches characters between P and Z, including P and Z.
Ex: PRIRIOTY
[^P-Z]-Matches characters except P to Z range.
Ex:PRIRIOTY
[P-Z p-z]-Matches characters between P-Z and p-z.
Ex:PQR3434pqr
\A - Matches the starting of the line. Not effecting the multiline mode.
Ex: \ABob - Bob is good.
\b - Matches position at a word boundary
Ex: \bGumm - Gummadi shiGumm Gumm
Gumm\b - Gummadi shiGumm Gumm
\bGumm\b - Gummadi shiGumm Gumm
\B matches exactly opposite to \b
Ex: \BGumm - Gummadi shiGumm Gumm
\d - Matches digits.
Ex:123abc
\D - Matches all except digits.
Ex:123abc
\s - Matches any space , tab or newline character.
Ex:I am learning Regex
\S - Matches all except space.
Ex: I am learning Regex
\w - Matches letter , digit , underscore Equivalent to [a-zA-Z0-9_]. not matching special characters.
Ex: Shiva will get 10% _len
\W - Matching anything other than letter , digit , underscore.
Ex: Shiva will get 10% _len
\Z - Matches the end of the line. Not effecting the multiline mode.
Ex: Shiva\Z
Gummadidal Shiva
Regex classes by Gummadidal Shiva
. - Matches any character except line terminator.
Ex: Shiva
.. -Matches two - two letters
Ex: Shiva
| - Matches either left side or right side
Ex: s|g : gummadidala shiva
* - Matches zero or more characters.
Ex:PQ*- P PQQQ PRR
+ - Matches one or more characters.
Ex:PQ+ - P PQQQ PRR
{m} -Matches exactly m characters
Ex: Q{3}- P PQQQ PRR
Q{3,} - P PQQQ PRR QQ QQQQ minimum = 3 , maximum >3
Q{3,4} - P PQQQ PRR QQ QQQQ QQQQQ minimum = 3 , maximum = 4
$ - Matches the end of the line.effecting the multiline mode.
Ex: Shiva$
Gummadidal Shiva
Regex classes by Shiva. Shiva is good teacher
Thanks to Shiva
Regular Expression Options :
Using Regular expression options changing scope and visibility of the pattern.
Flag Behavior
i Case - insensitive matching
m (Multiline)Matching pattern text in multiple lines where (^ , $ represent the beginning and end of the line)
s (Single line)Matching pattern text in single line
n (ExplicitCapture) Do not capture unnamed groups.
x (IgnorePatternWhiteSpace) Exclude unescaped white space
Operators precedence in Regular Expressions
For Regex interview questions click here
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