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| Volume Management Library Functions | media_getattr(3VOLMGT) |
| | media_getattr, media_setattr - get and set media attributes |
SYNOPSIS
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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); |
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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 slice numbers | list of partitions on this volume |
| s-location | RO | pathname | Volume Management pathname 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.
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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.
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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:
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ENXIO
- The Volume Management daemon, vold, is not running
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EINTR
- The routine was interrupted by the user before finishing
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| | Example 1. Using media_getattr
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The following example checks to see if the volume called fred that Volume Management is managing can be ejected by means of software, or if it can only be manually ejected:
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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");
}
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This example shows setting the s-enxio property for the floppy volume currently in the first floppy drive:
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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");
}
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See attributes(5) for descriptions of the following
attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
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cc(1B), vold(1M), lstat(2), open(2), readlink(2), stat(2), free(3C), malloc(3C), media_findname(3VOLMGT), volmgt_check(3VOLMGT), volmgt_inuse(3VOLMGT), volmgt_root(3VOLMGT), volmgt_running(3VOLMGT), volmgt_symname(3VOLMGT), attributes(5)
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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)).
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