What is the exit code of a C# program that throws an exception out of main?

Question

In a C# program, what is the exit code defined to be when an exception in thrown out of main? I know you can set the exit code in a number of ways as documented in this excellent answer. But I'm very surprised that I can't find documentation for what the value of the exit code is defined to be when an exception is thrown out of main. Is there a standard that defines what the value of the exit code will be in this case, or does it depend upon the operating system (or chance, or anything else)?

Answer 1

I observe -532462766

PS C:\Projects\Throw\Throw\bin\Debug> .\Throw.exe

Unhandled Exception: System.Exception: Exception of type 'System.Exception' was thrown at Throw.Program.Main(String[] args) in c:\Projects\Throw\Throw\Program.cs:line 13

PS C:\Projects\Throw\Throw\bin\Debug> $LASTEXITCODE
-532462766

Answer 2

If you are looking for a successful exit, I would look for only zero. Zero is the standard "everything was good" code. In Dot net for Windows, from my experience, any non - handled exceptions will cause a negative exit code (I believe the number is based on the exception type). There are no negative exit codes in Linux / BSD (aka MAC), so I would assume that unhandled exceptions are 255 (IIRC, the "We don't know exactly broke, but something did break" code.

So, if you are looking for a cross - platform solution, just consider error code != 0 a failure.

Answer 3

The user handles it. Open a cmd prompt window, run a program yourblahprogram<ENTER> do echo %ERRORLEVEL%

0 signifies no error. non zero indicates error.

i'll use DIR but you can use your program

C:\Users\user\aa\a>dir
 Volume in drive C has no label.
 Volume Serial Number is B411-D580

 Directory of C:\Users\user\aa\a

03/04/2017  11:11 PM    <DIR>          .
03/04/2017  11:11 PM    <DIR>          ..
               0 File(s)              0 bytes
               2 Dir(s)  15,943,544,832 bytes free

C:\Users\user\aa\a>echo %ERRORLEVEL%
0

C:\Users\user\aa\a>dir sdsklfjdlkdfjs
 Volume in drive C has no label.
 Volume Serial Number is B411-D580

 Directory of C:\Users\user\aa\a

File Not Found

C:\Users\user\aa\a>echo %ERRORLEVEL%
1

C:\Users\user\aa\a>

And you can act based on it

C:\Users\user>if NOT ERRORLEVEL 0  echo asdf

though actually teh above isn't that good 'cos it only works well when the errorlevel is negative.. 'cos NOT ERRORLEVEL 0 means not >=0. As you see from If /? and from Foolproof way to check for nonzero (error) return code in windows batch file

so this would be better if not errorlevel 0. IF %ERRORLEVEL% NEQ 0 echo asdf

so if your code does throw new System.Exception();

C:\Users\user>a.exe
asdf

Unhandled Exception: System.Exception: Exception of type 'System.Exception' was thrown.
   at CustomMath.Main()

C:\Users\user>echo %ERRORLEVEL%
-532462766

C:\Users\harvey>

So you can act on that.

Besides if in windows cmd batch script, there is also && and ||

So let's say the program does WriteLine("asdf"); and throws an exception.

This means run the first thing to the left of the && and if it returns no error i.e. errorlevel 0, then run second thing, to the right. So you see that first example doesn't run echo qwerty, it doesn't display qwerty.

C:\Users\user>a.exe && echo qwerty
asdf

Unhandled Exception: System.Exception: Exception of type 'System.Exception' was thrown.
   at CustomMath.Main()

Now look at the second example. The || is OR, So it will run if either the left hand side or the right hand side is true, but it will be efficient so as soon as one of the sides is true it will complete. The left hand side runs first, and fails, so it continues and runs the right hand side, and will show qwerty.

C:\Users\user>a.exe || echo qwerty
asdf

Unhandled Exception: System.Exception: Exception of type 'System.Exception' was thrown.
   at CustomMath.Main()
qwerty

C:\Users\user>

So, you use your OS to handle it.

It'd be different, but similar, on linux.