How to use redirection in C for file input

c input io-redirection
Dexter picture Dexter · Oct 19, 2013 · Viewed 54.4k times · Source

I need to get the file from the terminal, I know the command will look like:

./a.out < fileName.txt

I'm not sure how to use fgets() in my program to use the file requested from the terminal.

Answer

Nigel Harper picture Nigel Harper · Oct 19, 2013

Using redirection sends the contents of the input file to stdin, so you need to read from stdin inside your code, so something like (error checking omitted for clarity)

#include <stdio.h>

#define BUFFERSIZE 100

int main (int argc, char *argv[])
{
    char buffer[BUFFERSIZE];
    fgets(buffer, BUFFERSIZE , stdin);
    printf("Read: %s", buffer);
    return 0;
}

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