Go (RE2)

Log4j Pattern Layout Token in GO

Match Log4j / Logback PatternLayout conversion specifiers like `%d{yyyy-MM-dd}`, `%-5p`, or `%c{1}`.

Try it in the GO tester →

Pattern

regexGO
%(?:-?\d+)?(?:\.\d+)?[a-zA-Z](?:\{[^}]*\})?   (flags: g)

Go (RE2) code

goGo
package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`%(?:-?\d+)?(?:\.\d+)?[a-zA-Z](?:\{[^}]*\})?`)
	input := `%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1} - %m%n`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

How the pattern works

% starts a conversion specifier. (?:-?\d+)? optionally matches a width modifier (negative for left-justify). (?:\.\d+)? optionally matches a max-width. [a-zA-Z] captures the conversion letter (d=date, p=priority, c=category, m=message, n=newline, etc.). (?:\{[^}]*\})? optionally matches a parameter in braces.

Examples

Input

%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1} - %m%n

Matches

  • %d{yyyy-MM-dd HH:mm:ss}
  • %-5p
  • %c{1}
  • %m
  • %n

Input

%t %p

Matches

  • %t
  • %p

Input

no log4j tokens

No match

—

Same pattern, other engines

JavaScript / ECMAScript

Supported

See how this pattern looks (and behaves) in JavaScript's built-in RegExp.

Python (re)

Supported

See how this pattern looks (and behaves) in Python's stdlib `re` module.

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