REXX - TRACE command

TRACE is an interactive debugging facility

Syntax : TRACE

A - All => Traces all clauses before execution
C - Commands => Traces all commands before execution
E - Error => Traces any command resulting in an error
F - Failure => Traces any command resulting in a failure . This is same as 'Normal'.
I - intermediates => Traces all clauses along with the intermediate results during evaluation of expressions and substituted names
L - Labels => Traces any labels passes during execution
N - Normal => Traces any command resulting in a negative return code after execution. This is the default setting
O - Off => Traces nothing
R - Results => Traces all clauses before execution. Displays final results of evaluating an expression
S - Scan => Traces all remaining clauses in the data without them being processed

Prefix:

! - inhibits host command execution.
Ex: TRACE !C => Causes commands to be traced but not processed. As each cmd is bypassed, the REXX RC is set to zero. You can switch off command inhibition, when it is in effect, by issuing a TRACE instruction with a prefix "!."

? - Controls interactive debug.
During usual execution, a TRACE option with a prefix of ? causes interactive debug to be switched on.