View exit code of a program (After the program exited)

Question

Lets say a program that outputs a zero in case of success, or 1 in case of failure, like this:

main () {
    if (task_success())
        return 0;
    else
        return 1;
}

Similar with Python, if you execute exit(0) or exit(1) to indicate the result of running a script. How do you know what the program outputs when you run it in shell. I tried this:

./myprog 2> out

but I do not get the result in the file.

Answer 1

There's a difference between an output of a command, and the exit code of a command.

What you ran ./myprog 2> out captures the stderr of the command and not the exit code as you showed above.

If you want to check the exit code of the a program in bash/shell you need to use the $? operator which captures the last command exit code.

For example:

./myprog 2> out
echo $?

Will give you the exit code of the command.

顺便说一句，为了捕获命令的输出，您可能需要使用捕获stdout和捕获stderr1作为重定向。12