This function will yield the return code of a child process only once. A subsequent call without an intervening EXEC (Int 21H Function 4BH) will not necessarily return any valid information.Used by a parent process, after the successful execution of an EXEC call (Int 21H Function 4BH), to obtain the return code and termination type of a child process.
Call with:
AH = 4DH
Returns:
AH = exit type
00H if normal termination by Int 20H, Int 21H Function
00H, or Int 21H Function 4CH
01H if termination by user's entry of CtrlDC
02H if termination by critical-error handler
03H if termination by Int 21H Function 31H or Int 27H
AL = return code passed by child process (0 if child terminated
by Int 20H, Int 21H Function 00H, or Int 27H)
Notes:
This function will yield the return code of a child process only once. A subsequent call without an intervening EXEC (Int 21H Function 4BH) will not necessarily return any valid information.
This function does not set the carry flag to indicate an error. If no previous child process has been executed, the values returned in AL and AH are undefined.
Example:
Get the return code and termination kind of child process that was previously executed with Int 21H Function 4BH (EXEC).
retcode dw ? ; return code, termination type
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mov ah,4dh ; function number
int 21h ; transfer to MS-DOS
mov retcode,ax ; save child process info
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