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Manual page for media_getattr(3X)

media_getattr, media_setattr - get and set media attributes

SYNOPSIS

cc [ flag... ] file... -lvolmgt [ library.... ]

#include <volmgt.h>

char *media_getattr(char *vol_path, char *attr);

int media_setattr(char *vol_path, char *attr, char *value);

MT-LEVEL

MT-Safe

DESCRIPTION

media_setattr() and media_getattr() respectively set and get attribute-value pairs (called properties) on a per-volume basis.

Volume Management supports system properties and user properties. System properties are ones that Volume Management predefines. Some of these system properties are writable, but only by the user that owns the volume being specified, and some system properties are read only:

 Attribute     Writable            Value             Description
------------------------------------------------------------------
s-access       RO         "seq", "rand"             sequential or
                                                    random access
s-density      RO         "low", "medium", "high"   media density
s-parts        RO         comma separated list of   list of par
                          slice numbers             titions on
                                                    this volume
s-location     RO         pathname                  Volume Mana
                                                    gement path
                                                    name to media
s-mejectable   RO         "true", "false"           whether or
                                                    not media is
                                                    manually
                                                    ejectable
s-rmoneject    R/W        "true", "false"           should media
                                                    access points
                                                    be removed
                                                    from database
                                                    upon ejection
s-enxio        R/W        "true", "false"           if set return
                                                    ENXIO when
                                                    media access
                                                    attempted

Properties can also be defined by the user. In this case the value can be any string the user wishes.

RETURN VALUES

Upon successful completion media_getattr() returns a pointer to the value corresponding to the specified attribute. A null pointer is returned if the specified volume doesn't exist, if the specified attribute for that volume doesn't exist, if the specified attribute is boolean and its value is false, or if malloc.3c fails to allocate space for the return value.

media_setattr() returns 1 upon success, and 0 upon failure.

ERRORS

Both media_getattr() and media_setattr() can fail returning a null pointer if an open.2 of the specified vol_path fails, if an fstat.2 of that pathname fails, or if that pathname is not a block or character special device.

media_getattr() can also fail if the specified attribute was not found, and media_setattr() can also fail if the caller doesn't have permission to set the attribute, either because it's is a system attribute, or because the caller doesn't own the specified volume.

Additionally, either routine can fail returning the following error values:

ENXIO: The Volume Management daemon, vold, is not running
EINTR: The routine was interrupted by the user before finishing

EXAMPLES

The following example checks to see if the volume called fred that Volume Management is managing can be ejected via software, or if it can only be manually ejected:

if (media_getattr("/vol/rdsk/fred", "s-mejectable") != NULL) {
        (void) printf("\"fred\" must be manually ejected\n");
} else {
        (void) printf("software can eject \"fred\"\n");
}

This example shows setting the s-enxio property for the floppy volume currently in the first floppy drive:

int     res;
 
if ((res = media_setattr("/vol/dev/aliases/floppy0", "s-enxio",
    "true")) == 0) {
        (void) printf("can't set s-enxio flag for floppy0\n");
}

NOTES

Upon success media_getattr() returns a pointer to a string which has been allocated, and should be freed when no longer in use (see free.3c

Last modified 21/April/97