Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

r"
"
gmix

Test String

Code Generator

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?mi)#Modifiers << NOT GOING TO DO THESE HERE. #∂ Before After Until in?Between #∂ onwards #Time-Time << Don't need as both times will match #Lonely HOURS List: 10,time or 12 <not going to do this # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # - - - - - - - - - - - BIG TIME REGEX - - - - - - - - - - - - #LONELY HOURS #These guys are just \d\d. So we identify them through proximity to known times (?: #Boundary Lookaround (?<=[ ]|^|[^\d\.:\r\n$£-]) #hour - you always have hours (?:1[0-9]|2[0-4]|0?[0-9]) (?: #Hour [or / to - , and] #People don't say "12pm or 3?" much. Build it if it comes up. (?:[ ]? (?:or|[,/-]|to|and) [ ]?) ) ){0,3} #TIME BASICS: #Basic times that are definitely times. Have to come last so longer strings match first. #Boundary Lookaround (BREAK THIS FOR THE LONELY NUMBERS) # (?<=[ ]|^|[^\d\.:\r\n$£-]) #hour - you always have hours ( (?:1[0-9]|2[0-4]|0?[0-9]) ) #Clarifier. Minutes, AM|PM, a TimeZone or a combination. ( #Minutes (?:[ ]?[\:\. ][ ]?) ([0-5][0-9]) #AM|PM | (?:[ ]?[ap]m|[ ]?o\'?[ ]?clock) #TimeZones | (?:[ ]? (?:PS?T|GMT|∆USA|∆US|ET|BST|∆UK |UK[ ]?[Tt]ime|[Ee]astern[ ]?[Tt]ime|[Pp]acific[ ]?[Tt]ime|[Cc]entral[ ]?[Tt]ime |∆UTC|ACDT|ACST|ACT|ACT|ADT|AEDT|AEST|AFT|AKDT|AKST|AMST|AMT|AMT|ART|AST|AST|AWDT |AWST|AZOST|AZT|BDT|BDT|BIOT|BRST|BRT|BST|BST|BST|BTT|CCT|CDT|CDT|CEDT|CEST|CET |CHADT|CHAST|CHOT|ChST|CHUT|CIST|CIT|CKT|CLST|CLT|COT|CST|CST|CST|CST|CST|CT|CVT |CWST|CXT|DAVT|DDUT|DFT|EASST|ECT|ECT|EDT|EEDT|EEST|EET|EGST|EGT|EIT|EST|EST|FET |FJT|FKST|FKST|FKT|FNT|GALT|GAMT|GFT|GILT|GIT|GMT|GST|GST|GYT|HADT|HAEC|HAST|HKT |HMT|HOVT|HST|IBST|ICT|IDT|IRDT|IRKT|IRST|IST|IST|IST|JST|KGT|KOST|KRAT|KST|LHST |LHST|LINT|MAGT|MART|MAWT|MDT|MET|MEST|MHT|MIST|MMT|MSK|MST|MST|MST|MUT|MVT|MYT|NCT |NDT|NFT|NPT|NST|NT|NUT|NZDT|NZST|OMST|ORAT|PDT|PETT|PGT|PHOT|PKT|PMDT|PMST|PONT |PST|PST|PYST|PYT|RET|ROTT|SAKT|SAMT|SAST|SBT|SCT|SGT|SLST|SRET|SRT|SST|SST|SYOT |TAHT|THA|TFT|TJT|TKT|TLT|TMT|TOT|TVT|ULAT|USZ1|UYST|UYT|UZT|VET|VLAT|VOLT|VOST |VUT|WAKT|WAST|WAT|WEDT|WEST|WET|WST|YAKT)\b ) #Now enable the combo. Note ideally we would say "use one of each" e.g., =/10:234210 ){1,3} #Lonely HOURS: List of Military times <Here we have enough info to allow no ":". |( (?: #Boundary Lookaround (?<=[ ]|^|[^\d\.:\r\n$£-]) #Must open with a military time, no "445" must be "0445" (?:1[0-9]|2[0-4]|0[0-9]) (?:[ ]?[0-5][0-9][ ]?) #or and (?:[ ]? (?:or|[,/-]|to|and) [ ]?) #2-4 military times, including the closing one ){1,3} #Must also end with a military time (?:1[0-9]|2[0-4]|0[0-9]) (?:[ ]?[0-5][0-9][ ]?) ) #Post rationalise the boundary criteria (?:\b|$|,\b)`) var str = `NEW TIME MATCHING REGEX *** REGEX 1: LONELY NUMBERS *** 12 or 3pm 4/5CET 5-6pm 2,4,5pm 1,3 or 6pm OK. 1,2,3 and 5pm are available 12pm or 3pm <Shouldn't match "or" #Military times 1200 or 1300. 1100,1300 or 1400. 121212121212121212 <don't match *** REGEX 2: BASICS *** 1 11am or 2pm 12pm 12 CET 12pm CET 12.32pm 14 pm 10.00? 0.15 3 : 34 10 53 00.15 at3.00? 10amis good for me 4 oclock 2o'clock 2 o clock yes,3 am 12.50 GBP USD 4.00 £12.50 10.93? 00000 0000-559 00001 00001 00001 01300 01700 from 2 - 6 there is about 3 of them Not sure, maybe 14 apples? how about 10 tomorrow? << should fail 10 tomorrow? about £23.00 10,11 or 12 10, 11 or 2? 10 or 12? 10 or my place? 1030 or 1130 10.30 or 12? 10 and 11 work 10, 11, 12th? 1,000 ` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Golang, please visit: https://golang.org/pkg/regexp/