Streams

Command Line Arguments

Starting a program by typing the name of the program at a prompt in a terminal or shell window is called "invoking the program from the command line."
When you use this method, you can also type in additional information, called command line arguments, that the program can use.
```
prog -v input.dat
```
Only text mode programs receive command line arguments; the graphics library that comes with this book does not collect them.
To receive command line arguments, you need to define the main function in a different way.
```
int main(int argc, char* argv[])
{
   . . .
}
```
- argc is the count of arguments.
- argv contains the values of the arguments.
Note that argc is an array of pointers to C character arrays.
In the invocation above, argc is 3 and argv contains (pointers to) the strings

argv[0]: "prog"

argv[1]: "-v"

argv[2]: "input.dat"
Note that argv[0] always points to the name of the program and that argc is always at least 1.