I'm working on a custom layout to mask sensitive information in our production logs. One of the key features is to use regular expressions - so i need the syntax of logback.xml to support the special characters in regex - including $. I have searched high and low with google - and read the source a bit.  but it looks like there is no mechanism to escape this character. Here is a fragment of my config file:  ...       <layout class="log.PIIFilterLayout">          <pattern>:%d{HH:mm:ss.SSS} [%thread] %-5level %logger{1} - %msg %n</pattern>          <!-- adhoc patterns -->           <regex>mdn='(.+)'</regex>          <regex>accountName=(.+)$</regex>... I have tried:   - $  - \$  - \\$  - $ No matter what - i get this:  Failed to instantiate [ch.qos.logback.classic.LoggerContext]Reported exception:java.lang.IllegalArgumentException: Failed to parse input [accountName=(.+)\\$] at ch.qos.logback.core.util.OptionHelper.substVars(OptionHelper.java:119) at ch.qos.logback.core.joran.spi.InterpretationContext.subst(InterpretationContext.java:159) at ch.qos.logback.core.joran.action.NestedBasicPropertyIA.body(NestedBasicPropertyIA.java:87) at ch.qos.logback.core.joran.spi.Interpreter.callBodyAction(Interpreter.java:295) at ch.qos.logback.core.joran.spi.Interpreter.characters(Interpreter.java:175) at ch.qos.logback.core.joran.spi.EventPlayer.play(EventPlayer.java:57) at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:149) at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:135) at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:99) at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:49) at ch.qos.logback.classic.util.ContextInitializer.configureByResource(ContextInitializer.java:75) at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:150) at org.slf4j.impl.StaticLoggerBinder.init(StaticLoggerBinder.java:85) at org.slf4j.impl.StaticLoggerBinder.<clinit>(StaticLoggerBinder.java:55) at org.slf4j.LoggerFactory.bind(LoggerFactory.java:129) at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:108) at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:302) at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:276) at util.LogFactory.getLogger(LogFactory.java:27) at log.PIITest.<clinit>(PIITest.java:20)Caused by: ch.qos.logback.core.spi.ScanException: Unexpected end of pattern string How can i escape $ in logback.xml? Paul