=====Reading the exit code of a DOS utility=====

//by Richard Russell, May 2006//\\ \\  BBC BASIC for Windows allows you to execute an external program using the ***RUN** command. The program can be a Windows //GUI program//, a Windows //console program// or an //MS-DOS program//. Both Windows console programs and MS-DOS programs have the ability to return an //exit code// which may, for example, indicate whether the program completed successfully or not. Listed below are three methods of discovering the exit code:
 
==== Method 1 ====

The routine below allows the exit code to be discovered by running the external utility via a //batch file//:

<code bb4w>
        F% = OPENOUT "RUN.BAT"
        PRINT #F%, program$ : BPUT #F%,10
        PRINT #F%, "ECHO %ERRORLEVEL% > EXITCODE.TXT" : BPUT#F%,10
        CLOSE #F%
        *RUN RUN.BAT
        F% = OPENIN "EXITCODE.TXT"
        INPUT #F%, exitcode$
        CLOSE #F%
        exitcode% = VAL(exitcode$)
</code>

The variable **program$** should contain the name of the external program plus any command line parameters it needs. Note that for this routine to execute correctly the //current directory// must be valid and writeable.\\ \\  Some standard DOS commands return exit codes which you may wish to test. For example the **XCOPY** command returns one of the following values:\\ 

  * 0: Files were copied without error.
  * 1: No files were found to copy.
  * 2: The user pressed CTRL+C to terminate xcopy.
  * 4: There is not enough memory or disk space, or syntax error.
  * 5: Disk write error occurred.

==== Method 2 ====

Run the external program using the function **FNexecuteandwait** which is documented in the article [[/Waiting%20for%20an%20external%20program%20to%20terminate|Waiting for an external program to terminate]] (scroll about two-thirds of the way down). The function returns the exit code.

==== Method 3 ====

by Jon Ripley, May 2006

Add code similar to the following to the initialisation routine of your program:

<code bb4w>
        SYS "GetModuleHandle", "MSVCRT.DLL" TO hdll%
        SYS "GetProcAddress", hdll%, "system" TO hsys%
</code>

Here **hdll%** the handle of the C run-time library used by the BBC BASIC interpreter and **hsys%** is a pointer to the //system()// function the library provides.\\ \\  To execute a command anywhere in your program use code similar to the following:

<code bb4w>
        SYS hsys%, program$ TO exitcode%
</code>

The variable **program$** should contain the name of the external program plus any command line parameters it needs. When the program returns **exitcode%** will contain the //exit code// of the program.