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I'm trying to write a program to read through a .ppm file and keep the data in a struct. To be able to do that though, I need to be able to open the file, which is not working so far. I'm obviously doing something wrong. Can you please take a look at the code and see if you can find out what's the problem? 

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

int readFile(char *filename);

int main(void)
{
    readFile("myfile.ppm");
    return 0;
}

int readFile(char *filename)
{
    int x = 0;
    FILE *pFile;
    pFile = fopen(filename, "rb");
    if(!pFile)
    {
        fprintf(stderr, "Unable to open file %s\n", filename);
        exit(1);
    }

    fscanf(pFile, "%d", &x);
    fclose(pFile);
    printf("%d\n", x);
    return 0;
}

This just gives me an "\n" on the stdout. Should I fscanf it into an array rather than an int?

Based on your feedback I edited the code to scanning to two chars:

int readFile(char *filename)
{
    char first, second = 0;
    FILE *pFile;
    pFile = fopen(filename, "rb");
    if(!pFile)
    {
        fprintf(stderr, "Unable to open file %s\n", filename);
        exit(1);
    }

    fscanf(pFile, "%c%c", &first, &second);
    fclose(pFile);
    printf("First: %c, Second: %c\n", first, second);
    return 0;
}
imre
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  • test the return value from `*scanf`: it should be the number of variables assigned a value. – pmg Mar 24 '14 at 22:12

1 Answers1

2

According to http://en.wikipedia.org/wiki/Netpbm_format the file starts with a two byte sequence: P1, P2, P3 (as Human readable Text - ASCII). So reading this into an int will not work. You should read in a char (for the P) and then another char for the number and to find out what format your file is. Then depending on the format take further steps.

Ferenc Deak
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