Reading command line arguments from stdin

Question

So I want to allow myself to run ./program so that it allows input for piping a text file.

EX: ./program < sometext.txt

I know that I can't get the data using argv, but I've been trying to google how to get it from stdin, and I can't seem to find the right keywords to google to get some basic understanding of how to do this. I'm sure it's done using scanf, but I still have a hard time trying to understand it.

Any sort of insight would be helpful, I don't need the exact code, though if it's simple enough, that would be very helpful. Thanks!

Answer 1

Here's a simple example (with no error checking) that reads stdin into a dynamically allocated character array and then prints it back to stdout:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    int bufferSize = 100;
    char *buffer = malloc(bufferSize);
    int length = 0;
    int c;

    while ((c = getchar()) != EOF)
    {
        if (length == bufferSize)
        {
            bufferSize *= 2;
            buffer = realloc(buffer, bufferSize);
        }

        buffer[length++] = c;
    }

    for (int j = 0; j < length; j++)
    {
        putchar(buffer[j]);
    }

    free(buffer);
    return 0;
}

Hopefully that will get you started.