Logsflags: g

Log4j Pattern Layout Token

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

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("%(?:-?\\d+)?(?:\\.\\d+)?[a-zA-Z](?:\\{[^}]*\\})?", "g");
const input = "%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1} - %m%n";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"%(?:-?\d+)?(?:\.\d+)?[a-zA-Z](?:\{[^}]*\})?")
input_text = "%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1} - %m%n"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

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.

Pattern

regexengine-agnostic

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

Raw source: %(?:-?\d+)?(?:\.\d+)?[a-zA-Z](?:\{[^}]*\})?

How it 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.