REg-EX
(the bare minimum)
A train leaving a station at 10:50pm from San Francisco is traveling at 40MPH. Another train leaving Chicago at 12:00pm is going 60MPH. At which point will the two trains cross paths.
ax + b = c
basic reg-ex symbols
Characters
cat matches 'cat' and 123 matches '123'
10 is two symbols 1 and 0
Parenthesis
(cat) is the same as cat
The Line Anchors: ‘^’ and ‘$’
^cat matches lines that start with blue 'cat pics'
cat$ matches lines that end with cat 'bobcat'
BASIC REG-EX SYMBOLS
The Character Class: ‘[]‘
gr[ea]y matches 'grey' or 'gray'
[0-9] matches 1,2,3....9
[^abc] matches anything except a,b,c
The dot
. matches any single character a,x,6,0 except line breaks
[.] or \. matches .
The Alternation : ‘|’
cat|dog matches cat or dog
Mi(ke|chael) matches Mike or Michael
BASIC REG-EX SYMBOLS
The Optional match: '?'
flavou?r matches 'flavour' or 'flavor'
Quantifiers: ‘+’ and ‘*’
go+al means at least one 1 o goal or gooooooooal
go*al means 0 or more o gal, goal or goooooooal
Interval Quantifier: ‘{}’
go{1,3}al matches goal, gooal, goooal but not gooooal or gal
go{0,1}al === go?al
Escape character: '\'
what? matches wha but what\? matches what?
BASIC REG-EX SYMBOLS
\d A digit: [0-9]
\D A non-digit: [^0-9]
\s A whitespace character: [ \t\n\x0B\f\r]
\S A non-whitespace character: [^\s]
\w A word character: [a-zA-Z_0-9]
\W A non-word character: [^\w]
\b Word boundary
HANDS ON
Match user name
- alphabets, numbers and _ allowed
- must begin with any of those characters
- must have 3 to 16 characters in total
What does this match?
^#?([a-f0-9]{6}|[a-f0-9]{3})$
Java endsWith, startsWith, contains
- alphabets, numbers and _ allowed
- must begin with any of those characters
- must have 3 to 16 characters in total
What does this match?
^#?([a-f0-9]{6}|[a-f0-9]{3})$
Java endsWith, startsWith, contains
More hands on
| A?B? | |
| A|C | |
| B |
Match days of the week (ex: Mon, Tue, Wed ... )
The Giants In Tiny Pants Problem
Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.
(?:(?:rn)?[ t])*(?:(?:(?:[^()<>@,;:\".[] 000-031]+(?:(?:(?:rn)?[ t] )+|Z|(?=[["()<>@,;:\".[]]))|"(?:[^"r\]|\.|(?:(?:rn)?[ t]))*"(?:(?: rn)?[ t])*)(?:.(?:(?:rn)?[ t])*(?:[^()<>@,;:\".[] 000-031]+(?:(?:( ?:rn)?[ t])+|Z|(?=[["()<>@,;:\".[]]))|"(?:[^"r\]|\.|(?:(?:rn)?[ t]))*"(?:(?:rn)?[ t])*))*@(?:(?:rn)?[ t])*(?:[^()<>@,;:\".[] 000-0 31]+(?:(?:(?:rn)?[ t])+|Z|(?=[["()<>@,;:\".[]]))|[([^[]r\]|\.)*](?:(?:rn)?[ t])*)(?:.(?:(?:rn)?[ t])*(?:[^()<>@,;:\".[] 000-031]+ ... for 6343 characters ...
deck
By Pavan K Mutt
