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— Programming Guide —

Issuing Operating System Commands from within a Natural Program

The Natural user exit SHCMD can be used to issue an operating system command from within a Natural program.

This document covers the following topics:

Syntax
Parameters
Parameter Options
Return Codes
Examples

Syntax

CALL 'SHCMD' 'command' ['option']

Parameters

command

command is to be executed by the operating system. To execute commands (such as DIR for directory or DEL for delete) you have to specify the system command interpreter as well.

For more information, see Examples below.

option

option describes how the command should be executed. This parameter is optional. The following options are available:

ASYNCH
NOSCREENIO
SYNCH (default)

See Parameter Options below.

Parameter Options

The following parameter options are available:

Option	Description
`ASYNCH`	Natural does not wait until the command is completely executed. This kind of processing is named asynchronous processing.
`NOSCREENIO`	This option is used to hide the output generated by the command. The hidden output is redirected to the null device.
`SYNCH`	Natural waits until the command is completed. This kind of processing is named synchronous processing and is set by default.

Note:
The options ASYNCH and SYNCH may be not set at the same time.

Return Codes

The following return code values are available:

Return Code	Description
`0`	Command successfully executed.
`4`	Illegal SHCMD parameter specified.
All other codes	Operating-system-dependent error code.

Examples

Execute operating system command DIR to view a directory:

CALL 'SHCMD''CMD.EXE /C DIR'

Retrieve the return code by using the Natural function RET:

RESET rc (I4)  
CALL 'SHCMD''CMD.EXE /C DIR'  
rc = RET( 'SHCMD' )                   /* retrieve return code  
IF rc <> 0 THEN                       /* in case of an error  
DISPLAY "Error occurred during SHCMD" /* display an error message

Execute a command which includes blanks within the command by enclosing the command with quotation marks.

The following example executes Microsoft Excel.

RESET #cmd (A253)
MOVE '"C:\Program Files\Microsoft Office\Office\EXCEL.EXE"' to #cmd
CALL "SHCMD" #cmd "ASYNCH"

In this case, parameter TQ (translate quotation marks) has to be OFF, otherwise the quotation marks have been removed.

To be independent of the TQ parameter, use the hexadecimal ASCII code of quotation marks (H'22') and append it at the beginning and the end of the command. The following example demonstrates this:

RESET #cmd (A253)
MOVE H'22' - "C:\Program Files\Microsoft Office\Office\EXCEL.EXE" - H'22' to #cmd
CALL "SHCMD" #cmd "ASYNCH"

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