Z:gnu-bash--9e9120-Return the context of the curr/en

Return the context of the current subroutine call. Without EXPR, returns "$line $filename". With EXPR, returns "$line $subroutine $filename"; this extra information can be used to   provide a stack trace. The value of EXPR indicates how many call frames to go back before the current one; the top frame is frame 0. Exit Status: Returns 0 unless the shell is not executing a shell function or EXPR is invalid.