argv.md

What is argc?

The number of arguments which will be passed into a function.

What if I want the function to be variadic?

I don't know.

What is argv[0]?

The name of the program.

Why?

[see picture of process / memory organisation struct from mit xv6]

Have I seen this somewhere else?

Yes, in perl $0 is also the name of the program.

[ruby example?]

What is argv?

An array (=equal-length boxes stacked N long) containing the arguments which will be passed to the function.

What if I want the array to be variably-sized?

Then instead of {{type}} name[size], write {{type}} name[].

What is the standard format for int main?

#includes

//globals
//possibly functions


int main(int argc, char* argv[])
{
	//the program
	return(0);
	}

//maybe more functions

Why the return(0)?

[xv6 answer]

Is that really a function?

No, it's not a mathematical function. Computer people just like to mis-use maths words to intimidate you.

What's the larger context for these instructions?

The instructions sit in a plain text file. You need to "build" them into a program. Building them requires a lexer+tokenizer to scan the text, a compiler to turn the parsed text into something closer to computer instructions, and a linker (man ld, man ar, man nm) to bring stuff from various places (like #include <graphics.h> or #include <tty.h>) into the executable you're building.

This multi-step process might be driven by a Makefile. make is a scripting language with a horrendously long manual which nobody actually likes but which does the job of scanning for requirements and dependencies and then executing instructions only if a job actually needs to be done.

Why are there curly braces {} and semicolons ;?

It makes the job of scanning and tokenising your text instructions easier. If you didn't terminate a line with ; then the person writing the compiler would have to infer what you almost certainly meant (but remember, they wrote the compiler without talking to you or looking at your code).