check_usage(3)						     Library Functions Manual						    check_usage(3)

NAME

       check_usage - Checks whether a disk partition is in use

LIBRARY

       Filesystem Library (libfilsys.a)
       Shared Filesystem Library (libfilsys.so)

SYNOPSIS

       #include <sys/disklabel.h>
       #include <overlap.h>

       int check_usage(
	       const char *special,
	       int flag);

PARAMETERS

       Points to a special device file.  Specifies the scope of usage checking.  Valid values are: Checks the usage of the specified partition and
       all overlapping partitions.  Checks the usage of the specified partition only.

DESCRIPTION

       The check_usage function checks whether the special device file is in use, that is, whether it contains a valid file  system,  is  part	of
       LSM, or is being used by a database or for swap space.

       If  the	flag  OV_CHECK_ALL  is	set,  check_usage() also checks to ensure that the range of blocks to be used does not overlap with blocks
       already in use or marked to be in use by an overlapping partition.

       If the flag OV_CHECK_EXACT is set, usage checking is limited to the specified partition only.

       The check_usage function checks whether the special device file is in use by comparing it with all  mounted  file  systems  (both  UFS  and
       AdvFS),	swap devices, and LSM disks. It also reads the disk label to check the fstype field of the specified partition and any overlapping
       partitions. If any partition is marked as being in use, the appropriate error is returned.

       Before allocating a partition, an application should check that none of the overlapping partitions is in use. When an  application  uses  a
       partition, it should mark its use by setting the fstype field in the partition map in the disk label.

       See <sys/disklabel.h> for a list of the supported file system types that can be set using the set_usage() function.

EXAMPLES

       The  following  function  illustrates the use of check_usage() and possible error messages that could be printed based on the return values
       from check_usage().  #define DKTYPENAMES #include <stdio.h> #include <sys/disklabel.h> #include <overlap.h>

       #define STR_ERR_OPEN 
	   "Error: %s is open and in use.
"

       #define STR_ERR_OPEN_OVERLAP 
	   "Error: Partition overlapping %s is open and in use.
"

       #define STR_ERR_INVALID_DEV 
	   "Error: %s is an invalid device or cannot be opened.
"

       #define STR_ERR_DEFAULT_FSTYPE 
	   "Error: %s is marked in the disk label as in use by %s.
"

       #define STR_WARN_FSTYPE_OVERLAP 
	   "Warning: partition(s) which overlaps %s are marked in use.
"

       #define STR_WARN_MULT_OVERLAP 
	   "Warning: %s and overlapping partition(s) are marked in use.
"

       #define STR_WARN_INVAL_DISKLBL 
	   "Warning: the disklabel for %s does not exist or is corrupted.
"

       int get_usage(char *special) {
	   int	  ret;

	   /*
	    * Check if the specific partition and any
	    * overlapping partition is in use.
	    */
	   ret = check_usage(special, OV_CHECK_ALL);

	   if (ret == 0) {
	       /*
		* Specified partition is available for use.
		*/
	       return (0);
	   } else {
		/*
		 * Specified partition has a valid fstype.
		 */
	       if ( (ret > 0) && (ret <= FSMAXTYPES) ) {
		   fprintf(stderr, STR_ERR_DEFAULT_FSTYPE,
		       special, fstypenames[ret]);
		   return(-1);
	       }
	   }
	   /*
	    * Print appropriate error messages for the rest of
	    * the return values.
	    */
	   switch (ret) {

	   case OV_ERR_OPEN_OVERLAP:
	       /*
		* Check if the specified partition is open.
		*/
	       ret = check_usage(special, OV_CHECK_EXACT);
	       if (ret == OV_ERR_OPEN_OVERLAP)
		   fprintf(stderr, STR_ERR_OPEN, special);
	       else
		   fprintf(stderr, STR_ERR_OPEN_OVERLAP, special);
	       break;
	   case OV_ERR_INVALID_DEV:
	       fprintf(stderr, STR_ERR_INVALID_DEV, special);
	       break;
	   case OV_ERR_INVALID_DSKLBL:
	       fprintf(stderr, STR_WARN_INVAL_DISKLBL, special);
	       break;
	   case OV_ERR_FSTYPE_OVERLAP:
	       fprintf(stderr, STR_WARN_FSTYPE_OVERLAP, special);
	       break;
	   case OV_ERR_MULT_FSTYPE_OVERLAP:
	       fprintf(stderr, STR_WARN_MULT_OVERLAP, special);
	       break;
	   }
	   return (-1); }

RETURN VALUES

       The check_usage function returns the values described here.  Logical names for the return values are listed in  parentheses.   Checks  suc-
       ceeded. The range of blocks is not open or marked for use.  Note that for the mount command, you get a warning message if the fstype is set
       to FS_UNUSED; it should be set to FS_BSDFFS.  Either the specified special device file or an overlapping partition is open  or  marked  for
       use.   Either  the special device file name is invalid or the device cannot be opened.  Overlapping partitions are marked for use, that is,
       they have a value set for fstype. Note that the command disklabel -s can be used to unset any partitions that should not be marked for use.
       The   specified	partition and overlapping partitions have the fstype field set.  The disk label is not present or is corrupted. You should
       install a disk label and set the fstype field of any partitions that are in use. You should correct any changes	to  the  partition  layout
       before trying to use the newfs command on a partition.  An error was encountered during the checks.  Either /etc/fdmns or /etc/fdmns/domain
       for an in-use domain does not exist or is corrupted.  An error was encountered during the checks.  The special device file  for	an  in-use
       swap  device  does  not exist.  This indicates a failure in updating the disk label.  The specified partition is set to an fstype, which is
       the return value.  Refer to <sys/disklabel.h> for information on valid fstype values.

RELATED INFORMATION

       Commands: disklabel(8)

       Functions: set_usage(3) delim off

																    check_usage(3)