c - Is returning zero from main necessary, and how can the return value from main be useful? -

I know that in C88 it always returns 0 integer value from main to a program, such as:

  int main () {/ * here is some useful / return 0; }  

This is to return the "successful" result to the operating system. I still consider myself a newbie (or best intermediate programmer) in C, but to date I have not fully understood why this is important.

My guess is, this is a useful return result if you are writing the output of this program in the form of another input, but I'm not sure. I have never found it useful, or maybe I did not understand what is the intention.

My question:

1. C program always needs to return zero
2. How to Return Value from Main () Useful?

While typing a script (such as Bash, or CMD.exa on Windows) Command & amp; Amp; Amp; And || Operators

Canonically, A & amp; Amp; B will run b if the result of a is zero, and a || B will run b if a will return to the noose.

This is useful if you wish to command a command, if the last one is successful. For example, if you want to delete the file, if the word is foo then you will use it:

  grep foo myfile & amp; Amp; RM myfile  

grep Returns 0 When a match occurs, and nozerz.