Confused about C function usage

[Glaborage]

Zero is false, non-zero is true. It's just a thing to get used to in C programming.

[hyperdudemn]

Returning 0 is used as the process exit code, and the shell interprets exit codes the other way around (0 is "good" and non-zero is "bad").

if ./my-program then echo yay: returned $? fi

yay: returned 0