title: Why am I getting "Segmentation Fault" when I run my program?
body: <p>My program decodes an image that is covered by random pixels, to decode the image, I have to multiply each pixel's red color component by 10. The green and blue color components are the same values as the new red component. I've created multiple helper functions, to make the code easier to read in main, but when I try to run my a.out, I keep getting "Segmentation Fault". I can't seem to find my mistakes! Help is appreciated.</p>
  
  <pre><code>void check_argument(int arg_list)
  {
     if (arg_list &lt; 2)
     {
        perror("usage: a.out &lt;input file&gt;\n");
     }
  }
  
  void print_pixel(int a, FILE *out)
  {
     int r, g, b;
  
     r = a * 10;
  
     if (r &gt; 255)
     {
        r = 255;
     }
  
     g = r;
     b = r;
  
     fprintf(out, "%d\n", r);
     fprintf(out, "%d\n", g);
     fprintf(out, "%d\n", b);
  }
  
  void read_header(FILE *in)
  {
     char str[20];
  
     for (int i = 0; i &lt; 3; i++)
     {
        fgets(str, 20, in);
     }
  }
  
  FILE*  open_files(FILE *infile, char *input[])
  {
     infile = fopen(input[1], "r");
  
     if (infile == NULL)
     {
        perror("Error: Cannot read file.\n");
     }
  
     return infile;
  }
  
  void decode(int arg_list, char *in[])
  {
     FILE *input, *output;
  
     int check, red, green, blue;
  
     open_files(input, in);
     output = fopen("hidden.ppm", "w");
  
     fprintf(output, "P3\n");
     fprintf(output, "%d %d\n", 500, 375);
     fprintf(output, "255\n");
  
     read_header(input);
     check = fscanf(input, "%d %d %d", &amp;red, &amp;green, &amp;blue);
  
     while (check != EOF)
     {
        print_pixel(red, output);
        check = fscanf(input, "%d %d %d", &amp;red, &amp;green, &amp;blue);
     }
  
     fclose(input);
     fclose(output);
  }
  
  int main(int argc, char *argv[])
  {
     check_argument(argc);
     decode(argc, argv);
  }
  </code></pre>