HP OpenVMS Systems Documentation

Terminates processing of a command procedure or subroutine and returns control to the calling command level---either an invoking command procedure or interactive DCL. The EXIT command also terminates an image normally after a user enters Ctrl/Y (executing another image has the same effect).

Format

EXIT [status-code]

Parameter

status-code

Defines a numeric value for the reserved global symbol $STATUS. You can specify the status-code parameter as an integer or an expression equivalent to an integer value. The value can be tested by the next outer command level. The low-order 3 bits of the value determine the value of the global symbol $SEVERITY.

If you specify a status code, DCL interprets the code as a condition code. Note that even numeric values produce warning, error, and fatal error messages, and that odd numeric values produce either no message or a success or informational message.

If you do not specify a status code, the current value of $STATUS is saved. When control returns to the outer command level, $STATUS contains the status of the most recently executed command or program.

Description

The EXIT and STOP commands both provide a way to terminate the execution of a procedure. The EXIT command terminates execution of the current command procedure and returns control to the calling command level. If you enter the EXIT command from a noninteractive process (such as a batch job), at command level 0, then the process terminates.

The STOP command returns control to command level 0, regardless of the current command level. If you execute the STOP command from a command procedure or from a noninteractive process (such as a batch job), the process terminates.

When a DCL command, user program, or command procedure completes execution, the command interpreter saves the condition code value in the global symbol $STATUS. If an EXIT command does not explicitly set a value for $STATUS, the command interpreter uses the current value of $STATUS to determine the error status.

The low-order 3 bits of the status value contained in $STATUS represent the severity of the condition. The reserved global symbol $SEVERITY contains this portion of the condition code. Severity values range from 0 to 4, as follows:

Value	Severity
0	Warning
1	Success
2	Error
3	Information
4	Severe (fatal) error

Note that the success and information codes have odd numeric values, and that warning and error codes have even numeric values.

When any command procedure exits and returns control to another level, the command interpreter tests the current value of $STATUS. If $STATUS contains an even numeric value and if its high-order bit is 0, the command interpreter displays the system message associated with that status code, if one exists. (If no message exists, the message NOMSG will be displayed.) If the high-order bit is 1, the message is not displayed.

When a command procedure exits following a warning or error condition that has already been displayed by a DCL command, the command interpreter sets the high-order bit of $STATUS to 1, leaving the remainder of the value intact. This ensures that error messages are not displayed by both the command that caused the error, and by the command procedure.

The EXIT command, when used after you interrupt an image with Ctrl/Y, causes a normal termination of the image that is currently executing. If the image declared any exit-handling routines, they are given control. This is in contrast to the STOP command, which does not execute exit-handling routines. For this reason, the EXIT command is generally preferable to the STOP command.

Examples

$ EXIT 1 
      

The EXIT command in this example exits to the next higher command level, giving $STATUS and $SEVERITY a value of 1.

$ ON WARNING THEN EXIT 
$ FORTRAN 'P1' 
$ LINK 'P1' 
$ RUN 'P1' 
      

The EXIT command in this example is used as the target of an ON command; this statement ensures that the command procedure terminates whenever any warnings or errors are issued by any command in the procedure.

The procedure exits with the status value of the command or program that caused the termination.

$ START: 
$        IF (P1 .EQS. "TAPE") .OR. (P1 .EQS. "DISK") THEN GOTO 'P1' 
$        INQUIRE P1 "Enter device (TAPE or DISK)" 
$        GOTO START 
$ TAPE: !  Process tape files 
   .
   .
   .
$        EXIT 
$ DISK:  ! Process disk files 
   .
   .
   .
$        EXIT 
 
      

The command procedure in this example shows how to use the EXIT command to terminate different command paths within the procedure. To execute the procedure, you must enter either TAPE or DISK as a parameter. The IF command uses a logical OR to test whether either of these strings was entered. If the result is true, the GOTO command branches to the corresponding label. If P1 was neither TAPE nor DISK, the INQUIRE command prompts for a correct parameter.

The commands following each of the labels TAPE and DISK provide different paths through the procedure. The EXIT command before the label DISK ensures that the commands after the label DISK are executed only if the procedure explicitly branches to DISK.

Note that the EXIT command at the end of the procedure is not required because the end of the procedure causes an implicit EXIT command. Use of the EXIT command, however, is recommended.

$ IF P1. EQS. "" THEN - 
     INQUIRE P1 "Enter filespec (null to exit)" 
$ IF P1 .EQS. "" THEN EXIT 
$ PRINT 'P1'/AFTER=20:00/COPIES=50/FORMS=6 
      

The command procedure in this example tests whether a parameter was passed to it; if the parameter was not passed, the procedure prompts for the required parameter. Then it retests the parameter P1. If a null string, indicated by a carriage return for a line with no data, is entered, the procedure exits; otherwise, it executes the PRINT command with the current value of P1 as the input parameter.

$ IF P1 .EQS. "" THEN INQUIRE P1 "Code" 
$ CODE = %X'P1' 
$ EXIT CODE 
      

The command procedure in this example, E.COM, illustrates how to determine the system message, if any, associated with a hexadecimal system status code. The procedure requires a parameter and prompts if none is entered. Then it prefixes the value with the radix operator %X and assigns this string to the symbol CODE. Finally, it issues the EXIT command with the hexadecimal value. The following example uses the procedure E.COM:

$ @E 1C %SYSTEM-F-EXQUOTA, exceeded quota

When the procedure exits, the value of $STATUS is %X1C, which equates to the EXQUOTA message. Note that you can also use the F$MESSAGE lexical function to determine the message that corresponds to a status code.

$ RUN MYPROG
[Ctrl/Y]
$ EXIT
      

In this interactive example, the RUN command initiates execution of the image MYPROG.EXE. Then pressing Ctrl/Y interrupts the execution. The EXIT command that follows calls any exit handlers declared by the image before terminating MYPROG.EXE.