Thread: Why does argc need to be 2?

I was looking through the tutorials for c, and I was on the one about command line processing. I believe it was #14, but I'm not sure.

The example was reading in a file, but it needed argc to be equal to 2 in order to work right. The example checked for that value and everything.

This website is not the first place I've seen someone write their code like that before.

My question is this: Why does it have to be exactly 2? Couldn't it be 1 instead? Possibly 3 or 4? But it would at least seem to me to be more reasonable to make sure the count is 1 instead of 2. Afterall file names don't always have white space in them.

The first argument is always the filename of the program, so if you wanted to act on one argument, say a number like 4, then argv would contain:-
argv[0] = "myprogram.exe"
argv[1] = "4"

So, two arguments it is.

You can have more args just program it as needed. You can also have no args.

int main(void)

just remember to make your prog handle the args you get.

Yes, argc and argv are only used as parameters of main and sent to the program via the command line, which is pretty cool when working in a DOS-based environment. So, when you type the following in the command line: "program.exe 1 2 3 4" it goes like this:
argc = 5
argv[0] = program.exe
argv[1] = 1
argv[2] = 2
argv[3] = 3
argv[4] = 4

Take care because the 1, 2, 3 and 4 entered are defined as char so if you want the program to operate with them as integer or real you have to convert it to int or float or whatever crosses your mind, but I'm sure you understood it after the first reply, the rest is just us quasi programmers huffing and puffing

Originally Posted by itsme86

So, like Prelude said, it's either the program name or an empty string.

Not quite. It either represents the program name or it is an empty string.

There are all sorts of possibilities in that, depending on how the word "represents" is interpreted. For example argv[0] can be any of these;

1) the unadorned name of the executable (eg "program")

2) the name of the executable file (eg "program.exe" under windows)

3) the fully qualified path of the executable file (eg "c:/directory/subdirectory/program.exe" or "C:\directory\subdirectory\program.exe" under windows, or drive:[directory.path]program.exe on an old VAX/VMS system).

4) an alias for the executable (eg several unix shells support aliases, and could be passed as argv[0] by the shell, rather than the actual name of the executable)

5) the name of something that is linked to the executable (eg symbolic links under unix: the name of the link can be passed as argv[0]).