errxit – Error exit code – Computer Science by Example

errxit – Error exit code

Write a program that reads a single integer from standard input. If the integer is negative, the program should exit with an error exit code (different than zero). If the integer is zero or positive, the program should exit with a success exit code (zero).

$ ./errxit && echo 'Ok'
-3
$ ./errxit && echo 'Ok'
3
Ok

Scoring

6/6: works

Hints

Exit codes are used to signalize to the operating system whether a program ran successfully or failed. For example, the GCC compiler returns 0 when compilation was successful and returns an error code otherwise. This is useful when the compiler is called from scripts.

On Linux, you can check the exit code from the command line by issuing the echo $? command or alternatively by running your program followed by && echo 'zero exit code' which is executed when the program returns 0.

In Python, you can use the function exit to control the exit code;
In C, the value of the return in main is the exit code;
In Haskell, you can use exitSuccess and exitFailure from System.Exit to control the exit code from the IO monad.

try first: erro hello-cmd

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