c - What are the arguments to main() for?

Question

Everytime I create a project (standard command line utility) with Xcode, my main function starts out looking like this:

int main(int argc, const char * argv[])

What's all this in the parenthesis? Why use this rather than just int main()?

Answer 1

main receives the number of arguments and the arguments passed to it when you start the program, so you can access it.

argc contains the number of arguments, argv contains pointers to the arguments. argv[argc] is always a NULL pointer. The arguments usually include the program name itself.

Typically if you run your program like ./myprogram

• argc is 1;
• argv[0] is the string "./myprogram"
• argv[1] is a NULL pointer

If you run your program like ./myprogram /tmp/somefile

• argc is 2;
• argv[0] is the string "./myprogram"
• argv[1] is the string "/tmp/somefile"
• argv[2] is a NULL pointer