JMeter functions are special values that can populate fields of any Sampler or other element in a test tree. A function call looks like this:${__functionName(var1,var2,var3)}Where '__functionName' matches the name of a function.Parentheses surround the parameters sent to the function, for example ${__time(YMD)} The actual parameters vary from function to function. Functions that require no parameters can leave off the parentheses, for example ${__threadNum}.If a function parameter contains a comma, then be sure to escape this with '\', otherwise JMeter will treat it as a parameter JMeter functions are special values that can populate fields of any Sampler or other element in a test tree. A function call looks like this:${__functionName(var1,var2,var3)}Where '__functionName' matches the name of a function.Parentheses surround the parameters sent to the function, for example ${__time(YMD)} The actual parameters vary from function to function. Functions that require no parameters can leave off the parentheses, for example ${__threadNum}.If a function parameter contains a comma, then be sure to escape this with '\', otherwise JMeter will treat it as a parameter