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   udev_device_ref    ( 3 )

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Имя (Name)

udev_device_new_from_syspath, udev_device_new_from_devnum,
       udev_device_new_from_subsystem_sysname,
       udev_device_new_from_device_id, udev_device_new_from_environment,
       udev_device_ref, udev_device_unref - Create, acquire and release
       a udev device object

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Синопсис (Synopsis)

#include <libudev.h>

       struct udev_device
                                                        *udev_device_new_from_syspath(struct udev *udev,
                                                        const char *syspath);

       struct udev_device
                                                       *udev_device_new_from_devnum(struct udev *udev,
                                                       char type,
                                                       dev_t devnum);

       struct udev_device
                                                                  *udev_device_new_from_subsystem_sysname(struct udev *udev,
                                                                  const char *subsystem,
                                                                  const char *sysname);

       struct udev_device
                                                          *udev_device_new_from_device_id(struct udev *udev,
                                                          const char *id);

       struct udev_device
                                                            *udev_device_new_from_environment(struct udev *udev);

       struct udev_device
                                           *udev_device_ref(struct udev_device *udev_device);

       struct udev_device
                                             *udev_device_unref(struct udev_device *udev_device);

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Описание (Description)

udev_device_new_from_syspath(), udev_device_new_from_devnum(),
       udev_device_new_from_subsystem_sysname(),
       udev_device_new_from_device_id(), and
       udev_device_new_from_environment() allocate a new udev device
       object and returns a pointer to it. This object is opaque and
       must not be accessed by the caller via different means than
       functions provided by libudev. Initially, the reference count of
       the device is 1. You can acquire further references, and drop
       gained references via udev_device_ref() and udev_device_unref().
       Once the reference count hits 0, the device object is destroyed
       and freed.

       udev_device_new_from_syspath(), udev_device_new_from_devnum(),
       udev_device_new_from_subsystem_sysname(), and
       udev_device_new_from_device_id() create the device object based
       on information found in /sys/, annotated with properties from the
       udev-internal device database. A syspath is any subdirectory of
       /sys/, with the restriction that a subdirectory of /sys/devices
       (or a symlink to one) represents a real device and as such must
       contain a uevent file.  udev_device_new_from_devnum() takes a
       device type, which can be b for block devices or c for character
       devices, as well as a devnum (see makedev(3)).
       udev_device_new_from_subsystem_sysname() looks up devices based
       on the provided subsystem and sysname (see
       udev_device_get_subsystem(3) and udev_device_get_sysname(3)) and
       udev_device_new_from_device_id() looks up devices based on the
       provided device ID, which is a special string in one of the
       following four forms:

       Table 1. Device ID strings
       ┌──────────────┬──────────────────────────┐
       │Example       │ Explanation              │
       ├──────────────┼──────────────────────────┤
       │b8:2          │ block device major:minor │
       ├──────────────┼──────────────────────────┤
       │c128:1        │ char device major:minor  │
       ├──────────────┼──────────────────────────┤
       │n3            │ network device ifindex   │
       ├──────────────┼──────────────────────────┤
       │+sound:card29 │ kernel driver core       │
       │              │ subsystem:device name    │
       └──────────────┴──────────────────────────┘

       udev_device_new_from_environment() creates a device from the
       current environment (see environ(7)). Each key-value pair is
       interpreted in the same way as if it was received in an uevent
       (see udev_monitor_receive_device(3)). The keys DEVPATH,
       SUBSYSTEM, ACTION, and SEQNUM are mandatory.

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Возвращаемое значение (Return value)

On success, udev_device_new_from_syspath(),
       udev_device_new_from_devnum(),
       udev_device_new_from_subsystem_sysname(),
       udev_device_new_from_device_id() and
       udev_device_new_from_environment() return a pointer to the
       allocated udev device. On failure, NULL is returned, and errno is
       set appropriately.  udev_device_ref() returns the argument that
       it was passed, unmodified.  udev_device_unref() always returns
       NULL.

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Смотри также (See also)

udev_new(3), udev_device_get_syspath(3), udev_device_has_tag(3),
       udev_enumerate_new(3), udev_monitor_new_from_netlink(3),
       udev_list_entry(3), systemd(1),

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