Loop: libblockdev Reference Manual for libblockdev 3.1.0.

## Loop Loop — plugin for operations with loop devices |

## Functions

gboolean | bd_loop_init ()
void | bd_loop_close ()
GQuark | bd_loop_error_quark ()
BDLoopInfo * | bd_loop_info ()
BDLoopInfo * | bd_loop_info_copy ()
void | bd_loop_info_free ()
gchar * | bd_loop_get_loop_name ()
gboolean | bd_loop_setup ()
gboolean | bd_loop_setup_from_fd ()
gboolean | bd_loop_teardown ()
gboolean | bd_loop_set_autoclear ()
gboolean | bd_loop_is_tech_avail ()

## Types and Values

#define | BD_LOOP_ERROR
enum | BDLoopError
| BDLoopInfo
enum | BDLoopTech
enum | BDLoopTechMode

## Includes

    #include <loop.h>

## Description

A plugin for operations with loop devices. All sizes passed in/out to/from the functions are in bytes.

## Functions

### bd_loop_init ()

    gboolean
    bd_loop_init (void);

Initializes the plugin. **This function is called automatically by the library's initialization functions.**

### bd_loop_close ()

    void
    bd_loop_close (void);

Cleans up after the plugin. **This function is called automatically by the library's functions that unload it.**

### bd_loop_error_quark ()

    GQuark
    bd_loop_error_quark (void);

[skip]

### bd_loop_info ()

    BDLoopInfo *
    bd_loop_info (const gchar *loop,
                  GError **error);

#### Parameters

loop | name of the loop device to get information about (e.g. "loop0") |
error | place to store error (if any). | [out][optional]

#### Returns

information about the `loop` device or `NULL` in case of error

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_QUERY`.

[transfer full]

### bd_loop_info_copy ()

    BDLoopInfo *
    bd_loop_info_copy (BDLoopInfo *info);

Creates a new copy of `info` .

[skip]

#### Parameters

info | `BDLoopInfo` to copy. | [nullable]

### bd_loop_info_free ()

    void
    bd_loop_info_free (BDLoopInfo *info);

Frees `info` .

[skip]

#### Parameters

info | `BDLoopInfo` to free. | [nullable]

### bd_loop_get_loop_name ()

    gchar *
    bd_loop_get_loop_name (const gchar *file,
                           GError **error);

#### Parameters

file | path of the backing file to get loop name for |
error | place to store error (if any). | [out][optional]

#### Returns

name of the loop device associated with the given `file`

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_QUERY`.

[transfer full]

### bd_loop_setup ()

    gboolean
    bd_loop_setup (const gchar *file,
                   guint64 offset,
                   guint64 size,
                   gboolean read_only,
                   gboolean part_scan,
                   guint64 sector_size,
                   const gchar **loop_name,
                   GError **error);

#### Parameters

file | file to setup as a loop device |
offset | offset of the start of the device (in `file` ) |
size | maximum size of the device (or 0 to leave unspecified) |
read_only | whether to setup as read-only (`TRUE`) or read-write (`FALSE`) |
part_scan | whether to enforce partition scan on the newly created device or not |
sector_size | logical sector size for the loop device in bytes (or 0 for default) |
loop_name | if not `NULL`, it is used to store the name of the loop device. | [optional][out]
error | place to store error (if any). | [out][optional]

#### Returns

whether the `file` was successfully setup as a loop device or not

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_CREATE`

### bd_loop_setup_from_fd ()

    gboolean
    bd_loop_setup_from_fd (gint fd,
                           guint64 offset,
                           guint64 size,
                           gboolean read_only,
                           gboolean part_scan,
                           guint64 sector_size,
                           const gchar **loop_name,
                           GError **error);

#### Parameters

fd | file descriptor for a file to setup as a new loop device |
offset | offset of the start of the device (in file given by `fd` ) |
size | maximum size of the device (or 0 to leave unspecified) |
read_only | whether to setup as read-only (`TRUE`) or read-write (`FALSE`) |
part_scan | whether to enforce partition scan on the newly created device or not |
sector_size | logical sector size for the loop device in bytes (or 0 for default) |
loop_name | if not `NULL`, it is used to store the name of the loop device. | [optional][out]
error | place to store error (if any). | [out][optional]

#### Returns

whether an new loop device was successfully setup for `fd` or not

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_CREATE`

### bd_loop_teardown ()

    gboolean
    bd_loop_teardown (const gchar *loop,
                      GError **error);

#### Parameters

loop | path or name of the loop device to tear down |
error | place to store error (if any). | [out][optional]

#### Returns

whether the `loop` device was successfully torn down or not

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_DESTROY`

### bd_loop_set_autoclear ()

    gboolean
    bd_loop_set_autoclear (const gchar *loop,
                           gboolean autoclear,
                           GError **error);

#### Parameters

loop | path or name of the loop device |
autoclear | whether to set or unset the autoclear flag |
error | place to store error (if any). | [out][optional]

#### Returns

whether the autoclear flag was successfully set on the `loop` device or not

Tech category: `BD_LOOP_TECH_LOOP`-`BD_LOOP_TECH_MODE_MODIFY`

### bd_loop_is_tech_avail ()

    gboolean
    bd_loop_is_tech_avail (BDLoopTech tech,
                           guint64 mode,
                           GError **error);

#### Parameters

tech | the queried tech |
mode | a bit mask of queried modes of operation (BDLoopTechMode) for `tech` |
error | place to store error (details about why the `tech` -`mode` combination is not available). | [out][optional]

#### Returns

whether the `tech` -`mode` combination is available -- supported by the plugin implementation and having all the runtime dependencies available

## Types and Values

### BD_LOOP_ERROR

    #define             BD_LOOP_ERROR

### enum BDLoopError

#### Members

BD_LOOP_ERROR_TECH_UNAVAIL |  |
BD_LOOP_ERROR_FAIL |  |
BD_LOOP_ERROR_DEVICE |  |

### BDLoopInfo

    typedef struct {
        gchar *backing_file;
        guint64 offset;
        gboolean autoclear;
        gboolean direct_io;
        gboolean part_scan;
        gboolean read_only;
    } BDLoopInfo;

#### Members

gchar *`backing_file`; | backing file for the give loop device; |
guint64 `offset`; | offset of the start of the device (in `backing_file` ); |
gboolean `autoclear`; | whether the autoclear flag is set or not; |
gboolean `direct_io`; | whether direct IO is enabled or not; |
gboolean `part_scan`; | whether the partition scan is enforced or not; |
gboolean `read_only`; | whether the device is read-only or not; |

### enum BDLoopTech

#### Members

BD_LOOP_TECH_LOOP |  |

### enum BDLoopTechMode

#### Members

BD_LOOP_TECH_MODE_CREATE |  |
BD_LOOP_TECH_MODE_DESTROY |  |
BD_LOOP_TECH_MODE_MODIFY |  |
BD_LOOP_TECH_MODE_QUERY |  |