Path: utzoo!mnetor!uunet!husc6!bu-cs!madd
From: madd@bu-cs.BU.EDU (Jim Frost)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Setting DOS errorlevel in C  (How?)
Message-ID: <20689@bu-cs.BU.EDU>
Date: 17 Mar 88 02:40:36 GMT
References: <4831@sigi.Colorado.EDU>
Reply-To: madd@bu-it.bu.edu (Jim Frost)
Followup-To: comp.sys.ibm.pc
Distribution: na
Organization: Boston University Distributed Systems Group
Lines: 41

In article <4831@sigi.Colorado.EDU> murillo@boulder.Colorado.EDU (Rodrigo Murillo) writes:
>Does someone out there know how to set the DOS errorlevel number
>in C?  I want to write a batch file that can branch according to the
>value of this number:
>
>     if errorlevel 1 echo Big...
>     if errorlevel 2 echo Bigger...
>     if errorlevel 3 echo Biggest.
>
>Please send code fragments if possible.

You're going to get a million of these, but I thought I'd add to your
mail.  The answer is so obvious that it's often missed.

DOS ERRORLEVEL is nothing but a check of the return code for a program
(as specified when function 4CH Terminate a program (EXIT) is called).

The IBM Disk Operating System Technical Manual says:

	Purpose:  Terminates the current process and transfers control
		  to the invoking process.

	On Entry	Register Contents
	AH		4CH
	AL		Return code

	On Return	Register Contents
			NONE

	Remarks:  In addition, a return code can be sent.  The return
		  code can be interrogated by the batch subcommands IF
		  and ERRORLEVEL and by the wait function call 4DH.
		  All files opened by the process are closed.

In C on the PC, the return code is an optional argument to the exit()
command.  Thus, exit(2) will return ERRORLEVEL 2.

Happy hacking,

jim frost
madd@bu-it.bu.edu