Define a method which takes a givenBlock, invokes it with invokeAutoCollect and writes it to the log.

Code

define log(s) => { 
	local(f) = file
	handle => {#f->close}
	#f->openAppend(#s->asString)
	#f->writeString(givenBlock->invokeAutoCollect+sys_eol)
}

log('myfile.txt')
'The log message'
/log

Result

The string 'The log message' appended to the file 'myfile.txt'.