Example

   /*
    *   This is an example of using mrd_test_unit_ready(3mrd)
    *   to see if a media changer will accept commands.   On
    *   Digital UNIX this particular example will always
    *   succeed whether the robot is ready or not.  See the
    *   Restrictions section of the manual page for more
    *   information.
    *
    *   Usage:
    *
    *      mrd_test_unit_ready robot [ more-robots... ]
    */
   #ifndef   lint
   static char SccsId[] = "@(#)mrd_test_unit_ready.c   1.1 4/16/97" ;
   #endif

   #include <stdio.h>
   #include <stdlib.h>
   #include <string.h>
   #include <errno.h>
   #include <mrd_common.h>
   #include <mrd_message.h>

   /*
    *   Message string.
    */
   char *tur_failed_dev =
                "Test unit ready failed on %s: %s (%d,0x%x,0x%x).\n ";
   char *tur_failed_os  = "Test unit ready failed on %s: %s (%d).\n" ;
   char *tur_failed     = "Test unit ready failed on %s: %s.\n" ;

   /*
    *   The MRD can report three types of errors:
    *
    *   o  Device errors - When the "valid" field is set, at least one
    *      of the key, asc and ascq field should have values set from
    *      a SCSI Request Sense data or equivalent.
    *
    *   o  Operating System errors - When the valid field is zero, but
    *      the os_status field is set.  Where possible an MRD error
    *      will be set if one corresponds to the error.  If not, the
    *      MRD status will be MRD_STATUS_OS_ERROR.  The os_status
    *      is the error specific to the operating system.  On Digital
    *      UNIX it is an errno value.  On OpenVMS it is a system
    *      service return value.
    *
    *   o  MRD Errors - The MRD error code is set explicitly.
    */
   print_error(char *robot, int mrd_status, dev_status_t *dp)
   {
      /*
       *   Print the Key/ASC/ASCQ data for device errors.
       */
      if( dp->valid )
         printf(tur_failed_dev, robot, mrd_strstatus(mrd_status),
            dp->key, dp->asc, dp->ascq) ;
      /*
       *   Try to decode the os_status according to the operating
       *   system type.
       */
      else if( dp->os_status == MRD_STATUS_OS_ERROR )
         printf(tur_failed_os, robot, mrd_strstatus(mrd_status),
   #ifdef   unix
            strerror(dp->os_status)) ;
   #endif
   #ifdef   vms
            strerror(EVMSERR, dp->os_status)) ;
   #endif
      /*
       *   Just print the message on others.
       */
      else
         printf(tur_failed, robot, mrd_strstatus(mrd_status)) ;
   }

   main(int argc, char *argv[])
   {
      int      rc ;      /* counter */
      int      status ;   /* return status */
      char      *robot ;   /* Robot to open */
      robot_info_t   robot_info ;   /* Robot data */
      dev_status_t   dev_status ;   /* Device status */
      char      log_info[MRD_MAX_LOG_STRING+1] ;

      /*
       *   Check that there are enough arguments.
       */
      if( argc < 2 ) {
         printf("usage: %s robot [ robot... ]\n", argv[0]) ;
         exit(1) ;
      }

      /*
       *   Initialize the channel field of the robot_info, so
       *   mrd_startup(3mrd) will actually open the robot.
       */
      robot_info.channel = BAD_CHANNEL ;

      for(rc = 1; rc < argc; rc++) {
         /*
          *   The robot for this command.
          */
         robot = argv[rc] ;

         status = mrd_startup(robot, &robot_info, log_info) ;

         if( status != MRD_STATUS_SUCCESS ) {
            printf("Startup failed on %s: %s.\n", robot,
               mrd_strstatus(status)) ;

            continue ;
         }

         memset((void *)&dev_status, 0, sizeof(dev_status)) ;

         status = mrd_test_unit_ready(&robot_info, &dev_status) ;

         /*
          *   Do some fancy error printing.
          */
         if( status != MRD_STATUS_SUCCESS )
            print_error(robot, status, &dev_status) ;
         else
            printf("%s is ready.\n", robot) ;

         (void)mrd_shutdown(&robot_info) ;
      }

      return 0 ;
   }