Question

I am looking for a method to pull input into my program from either a Pipe from the terminal or by specifing a filename as an argument. Effectivly

1. foo | myprogram
OR
2. foo > bar; myprogram -w bar

The second operation is accoplished simply by reading the file. However I am drawing a blank on how to redirect the output from foo into myprogram with a pipe. In all the examples I have managed to find Pipes have been used almost exclusively for IPC from parent to child processes. Am I thinking of the proper Pipe or is this a different mechanism?

I also realize that when foo | myprogram is executed the programs are executed simulatniously. How is this handled if foo is read in continuously.

EDIT:

Forgot to include this:

int main(){
    char buff[255];
    int i = read(0, buff, 255);
    printf("Debug: %s\n", buff);
    return 0;
}

If for instance I execute ls | myprogram I tend to receive.

. ../ files
Debug: 

instead of

Debug: . ../ files

Answer 1

You can do something like this:

FILE* input;
//...
if (argc == 1) {
    input = stdin;
} else {
    input = fopen(argv[2] /* or whatever */, "r");
}