The PSL exit_status variable stores the exit status of a process
invoked from a system(), popen("OS",) or execute("OS",) function.
The user cannot write the exit_status variable.
Tip
The popen() function with an OS command type can set the
exit_status variable asynchronously whenever its operating system
child process dies. It is possible (although unlikely) that the popen()
function could set exit_status after a system() or execute()
function concludes but before exit_status is read for the system() or
execute() call.
Incompatibilities with the C Programming Language
There are features found in the C programming language that are not
supported by and not compatible with PSL. This section lists known
incompatibilities.
Operators && and
Difference: PSL does not perform short-circuit processing of the && and operators.
C Action: The && and functions short-circuit in standard C meaning that
evaluation stops with the first condition that establishes an outcome for
the statement. Some programmers use this feature to construct statements
that depend on the left-to-right sequential evaluation of the conditions.
PSL Action: PSL always evaluate all conditions in a statement using && and
operators. Evaluation of all conditions may cause unexpected results in
statements that depend on a left-to-right sequential evaluation and
short-circuit.
Prefix and Postfix Operators ++ and --
Difference: PSL does not distinguish between prefix and postfix operators.
C Action: Appending ++ or –– as a prefix instructs the program increment or
decrement the variable then test the condition, while appending ++ or ––
as a postfix instructs the program to test the condition before
incrementing or decrementing the variable.
PSL Action: PSL treats both prefix and postfix operators as prefix operators. Treating
postfix operators as if they were prefix operators may cause unexpected
results in statements that depend on postfix operators.
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Diagnosing PSL Program Errors 6-9
Break and Continue Statements
Difference: PSL supports the function but not the syntax of the break and
continue statements. PSL replaces the break statement with the last
statement, and the continue statement with the next statement.
PSL Action: PSL treats the C break and continue statements as statements that
evaluate the variable name break or continue and produce no output or
effect within the PSL program.