examples/open-qcow2.c

   1 /* This example shows how to use qemu-nbd
   2  * to open a local qcow2 file.
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8
   9 #include <libnbd.h>
  10
  11 int
  12 main (int argc, const char *argv[])
  13 {
  14   const char *filename;
  15   struct nbd_handle *nbd;
  16   char buf[512];
  17   FILE *fp;
  18
  19   if (argc != 2) {
  20     fprintf (stderr, "open-qcow2 file.qcow2\n");
  21     exit (EXIT_FAILURE);
  22   }
  23   filename = argv[1];
  24
  25   /* Create the libnbd handle. */
  26   nbd = nbd_create ();
  27   if (nbd == NULL) {
  28     fprintf (stderr, "%s\n", nbd_get_error ());
  29     exit (EXIT_FAILURE);
  30   }
  31
  32   /* Run qemu-nbd as a subprocess using
  33    * systemd socket activation.
  34    */
  35   char *args[] = {
  36     "qemu-nbd", "-f", "qcow2",
  37     (char *) filename,
  38     NULL
  39   };
  40   if (nbd_connect_systemd_socket_activation (nbd,
  41                                              args) == -1) {
  42     fprintf (stderr, "%s\n", nbd_get_error ());
  43     exit (EXIT_FAILURE);
  44   }
  45
  46   /* Read the first sector and print it. */
  47   if (nbd_pread (nbd, buf, sizeof buf, 0, 0) == -1) {
  48     fprintf (stderr, "%s\n", nbd_get_error ());
  49     exit (EXIT_FAILURE);
  50   }
  51
  52   fp = popen ("hexdump -C", "w");
  53   if (fp == NULL) {
  54     perror ("popen: hexdump");
  55     exit (EXIT_FAILURE);
  56   }
  57   fwrite (buf, sizeof buf, 1, fp);
  58   pclose (fp);
  59
  60   /* Close the libnbd handle. */
  61   nbd_close (nbd);
  62
  63   exit (EXIT_SUCCESS);
  64 }