libmagic

http://vivithemage.co.uk/blog/?p=105

A real nice article that go me started with using libmagic or magic.h.

<code>#include <stdio.h>

#include <magic.h>

 

int main(void)

{

    char *actual_file = "/file/you/want.yay";

    const char *magic_full;

    magic_t magic_cookie;

    /*MAGIC_MIME tells magic to return a mime of the file, but you can specify different things*/

    magic_cookie = magic_open(MAGIC_MIME);

        if (magic_cookie == NULL) {

            printf("unable to initialize magic library\n");

            return 1;

            }

        printf("Loading default magic database\n");

        if (magic_load(magic_cookie, NULL) != 0) {

            printf("cannot load magic database - %s\n", magic_error(magic_cookie));

            magic_close(magic_cookie);

            return 1;

        }

    magic_full = magic_file(magic_cookie, actual_file);

    printf("%s\n", magic_full);

    magic_close(magic_cookie);

        return 0;

}

</code>

To compile it do: "gcc magic_test.c -o magics -lmagic". Furthermore make sure the libmagic library is installed. "apt-get install libmagic-dev" should do it if you're using a machine with debian/ubuntu.

Below is my magic_buff testing:

<code>

#include <stdio.h>

#include <magic.h>

int main(void)

{

   printf("In main()\n");

   char *actual_file = "hello.c";

   const char *magic_full;

   magic_t magic_cookie;

   int BUF_SIZE = 8388608; // 2**23

   char buf[BUF_SIZE];

   magic_cookie = magic_open(MAGIC_MIME);

   if (magic_cookie == NULL)

   {

      printf("Unable to initialize magic library\n");

      return 1; 

   }

   if (magic_load(magic_cookie, NULL) != 0)

   {

      printf("Cannot load magic database - %s\n", magic_error(magic_cookie));

      magic_close(magic_cookie);

      return 1;

   }

   //magic_full = magic_file(magic_cookie, actual_file);

   magic_full = magic_buffer(magic_cookie, (const void *) &buf, BUF_SIZE);

   printf("%s\n", magic_full);

   magic_close(magic_cookie);

   return 0;

}

</code>