HP Pascal/iX Programmer's Guide (31502-90023)

11- 2
The procedure escape has one parameter, error_code , which is an integer
expression. Escape sets error_code , whose value you can then access with
the predefined function escapecode .
Example
PROGRAM p;
VAR
x : integer;
ecode : integer;
.
.
PROCEDURE PUTJCW; INTRINSIC;
PROCEDURE proc (n : integer);
BEGIN {proc}
{Test for erroneous parameter}
IF NOT (n IN [0..100]) THEN
escape(-755);
.
.
putjcw(jcwname,jcwvalue,error); {system call}
IF error > 0 THEN
escape(error); {system call failed}
.
.
END; {proc}
BEGIN {main program}
TRY
proc(x);
RECOVER
ecode := escapecode; {See note in "Escapecode Function"}
IF ecode = -775 THEN
{Report bad value of m}
ELSE IF ecode = -3550 THEN
{Report failure of system call}
ELSE
halt(ecode);
END. {main program}
Escapecode Function
The predefined function escapecode returns the integer value of
error_code , the parameter of the predefined procedure escape (see "Escape
Procedure" ).
The result of escapecode is undefined if escape was never called, and
after exit from the TRY-RECOVER construct by normal, sequential means
(rather than exit by explicit escape, exit, or goto ). If you call
escapecode when its result is undefined, the result is indeterminate and
meaningless. Access escapecode only in the RECOVER part of a TRY-RECOVER
construct.
To see the symbolic names for the escape codes that the Pascal
subsystem returns, list the file PASESC.PUB.SYS (on MPE/iX) or
/usr/include/pasesc.ph (on HP-UX).
TRY-RECOVER Construct
The TRY-RECOVER construct defines a group of statements as error recovery
code.
Syntax
TRY statement [; statement ]... RECOVER statement
Parameter
statement Labeled or unlabeled statement.
If an error occurs when the program executes a statement (or any routines
called by the statement in the TRY part):