>From the docs, $$ inside the <pattern> element:
1. <File name="Application" fileName="application.log"> 2. <PatternLayout> 3. <pattern>%d %p %c{1.} [%t] $${env:USER} %m%n</pattern> 4. </PatternLayout> 5. </File> Also from the docs, $ inside the header attribute: 1. <File name="Application" fileName="application.log"> 2. <PatternLayout header="${java:runtime} - ${java:vm} - ${java:os}"> 3. <Pattern>%d %m%n</Pattern> 4. </PatternLayout> 5. </File> I just read the docs on property substitution and how StrLookup treat variables with multiple leading '$' characters, but it is not obvious to me why in the two examples above, in one example two leading $ signs are used, and in the other only one $ is used. Best regards, Behrang Saeedzadeh