How do I use a text file passed in as an argument from the command line in C?

Question

I am having the hardest time trying to figure out how to use a text file that is passed in as a command line argument. I simply dont know to get the file text into my program to be used. My code looks something like this....

    char buffer[80];
    int i;
    int lineCount = 0;

    fgets(buffer, 80, stdin);  //get the first line

    while (buffer != NULL) {  
        // do some stuff
    }//end fgets while

This is for a homework assignment and I know my teacher is going to run the program with the following command:

    username@mylunixbox$ ./a.out <data1> output1

data1 is the text file I am trying to use.

Answer 1

int main(int argc, char **argv)
{
    int rc = EXIT_SUCCESS;
    for (int i = 1; i < argc; i++)
    {
        FILE *fp = fopen(argv[i], "r");
        if (fp == 0)
        {
            fprintf(stderr, "%s: failed to open file %s for reading\n",
                    argv[0], argv[i]);
            rc = EXIT_FAILURE;
        }
        else
        {
            char line[4096];
            while (fgets(line, sizeof(line), fp) != 0)
                ...do stuff with the line read from the file...
            fclose(fp);
        }
    }
    return rc;
}