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TRACE Statement Trace
Default value = FALSE. Determines whether statements are traced during
execution.
QTAwk has a facility for debugging programs. This facility is
activated through the built-in variable 'TRACE'. QTAwk can trace the
loop control statements, 'if', 'while', 'do', 'for' (both forms), and
'switch'. In addition, built-in functions and user-defined function
are traced.
By default, TRACE is FALSE and no tracing is done. The variable may be
set to any value, numeric, string or a regular expression and the value
will determine the statements traced. If TRACE has a nonzero numeric
value then QTAwk will trace all statements of the type listed. If
TRACE has a string value, then the string is compared against the
keywords:
if
while
do
for
switch
function_b ( for built-in functions )
function_u ( for user-defined functions )
If an exact match (case is important) is found, then the statement is
traced. If TRACE is set to a regular expression, then the keywords are
matched against the regular expression. If a match is found, then the
statement is traced.
In tracing a statement, QTAwk issues a message to the standard output
file "stdout". This file may be re-directed if desired. The message
issued will have the form:
Stmt Trace: stmt_str value_str
Action File line: xxxx
Scanning File: FILENAME
Line: xxxxx
Record: xxxxxx
where stmt_str is the appropriate keyword listed above for the
statement traced and value_str is a value dependent upon the statement
traced as listed below:
keyword value string
if ==> 0/1 conditional expression TRUE/FALSE
while ==> 0/1 conditional expression TRUE/FALSE
do ==> 0/1 conditional expression TRUE/FALSE
for ==> 0/1 conditional expression TRUE/FALSE
for ==> subscript value
switch ==> switch expression value
function_b ==> function name
function_u ==> function name
When a statement that can be traced is encountered, the value of the
statement is determined, e.g., for an 'if' statement, the value of the
conditional is evaluated before issuing the trace statement.
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