Regular Expressions 101

Explanation

Pro

^start of line

Negative Lookahead(?!.*\|\|)

.*any character (except for line terminators), repeated any number of times

\|the literal | (124₁₀ / 174₈ / 7C₁₆)

Negative Lookahead(?!.*[$^.?*+()A-Z])

.*any character (except for line terminators), repeated any number of times

Character Class[$^.?*+()A-Z]

$the literal $ (36₁₀ / 44₈ / 24₁₆)

^the literal ^ (94₁₀ / 136₈ / 5E₁₆)

.the literal . (46₁₀ / 56₈ / 2E₁₆)

?the literal ? (63₁₀ / 77₈ / 3F₁₆)

*the literal * (42₁₀ / 52₈ / 2A₁₆)

+the literal + (43₁₀ / 53₈ / 2B₁₆)

(the literal ( (40₁₀ / 50₈ / 28₁₆)

)the literal ) (41₁₀ / 51₈ / 29₁₆)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Negated Character Class[^\[\]\n]*

*matches any number of characters outside the set below:

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

\na line-feed (newline) character (ASCII 10)

Non-Capturing Group(?:\[[^\[\]\n]*\][^\[\]\n]*)*

*repeats the group contents below any number of times:

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

Negated Character Class[^\[\]\n]*

*matches any number of characters outside the set below:

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

\na line-feed (newline) character (ASCII 10)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

Negated Character Class[^\[\]\n]*

*matches any number of characters outside the set below:

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

\na line-feed (newline) character (ASCII 10)

Negated Character Class[^\[\]\n]*

*matches any number of characters outside the set below:

\[the literal [ (91₁₀ / 133₈ / 5B₁₆)

\]the literal ] (93₁₀ / 135₈ / 5D₁₆)

\na line-feed (newline) character (ASCII 10)

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

26 tokens

Regular Expression

^(?!.*\|\|)(?!.*[$^.?*+()A-Z])[^\[\]\n]*(?:\[[^\[\]\n]*\][^\[\]\n]*)*[^\[\]\n]*$

New

abcdef [ghijk] lmn
abcdef [ghijk] [pqr lmn
abcdef [pqr [ghijk] lmn
abcde| [ghijk] lmn
abcde| [ghijk] | lmn
abcde|| [ghijk] lmn
abcde? [ghijk] lmn








^(?!.*\[[^\]\n]*)[^$.|?*+()\n]*$

There should be no Capital letter in string.
String don't contains [^$.|?*+() with 2 exception. a. if there is [ in string then it will have to end with ] for example [test] is valid [test not valid, test] not valid [[test]] not valid etc. [test][test] can be valid.

^(?! [^\[\]\n]* (?:\[[^\[\]\n]*\][^\[\]\n]*)* \[ (?:\[[^\[\]\n]*\][^\[\]\n]*)*$)