Regular Expressions 101

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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"
"
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)(?P<assign_op>(\:|\!|\?)?=)|(?P<token_subst>$|%(\<\@))|(?P<token_ident>[\w\d\.\,]+)|(?P<target_name_match>%\.?)|(?P<token_rule_sep>[:])|(?P<incr_op>\n)|(?P<line_end>\n)|(?P<comment_op>#[.*]+$)|(?P<adjust_parser>[\$%\s\t\:])`) var str = `CC := nasm BOOT_REQ := text.o FREELDR_SRCS := freeldr.c IMG_NAME := boot.img TEXT_SECTION := 7c00 # UFS2, ZFS and/or RAW FILESYSTEMS := CPU_FLAGS := PAE SDK_FLAGS := VERSION := "1.00.00" %.o: $(ASM) ${SDK_FLAGS} -f bin -o $@ $(patsubst %.bin,%.asm,$@)) ${IMG_NAME}: $(BOOT_REQ) $(FREELDR_SRCS:.c=.o) ` 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/