1UDEV_DEVICE_NEW_FROM_SYSPAuTdHe(v3_)device_new_from_syUsDpEaVt_hDEVICE_NEW_FROM_SYSPATH(3)
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NAME

6       udev_device_new_from_syspath, udev_device_new_from_devnum,
7       udev_device_new_from_subsystem_sysname, udev_device_new_from_device_id,
8       udev_device_new_from_environment, udev_device_ref, udev_device_unref -
9       Create, acquire and release a udev device object
10

SYNOPSIS

12       #include <libudev.h>
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14       struct udev_device *udev_device_new_from_syspath(struct udev *udev,
15                                                        const char *syspath);
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17       struct udev_device *udev_device_new_from_devnum(struct udev *udev,
18                                                       char type,
19                                                       dev_t devnum);
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21       struct udev_device
22                                                                  *udev_device_new_from_subsystem_sysname(struct udev *udev,
23                                                                  const char *subsystem,
24                                                                  const char *sysname);
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26       struct udev_device *udev_device_new_from_device_id(struct udev *udev,
27                                                          const char *id);
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29       struct udev_device
30                                                            *udev_device_new_from_environment(struct udev *udev);
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32       struct udev_device *udev_device_ref(struct udev_device *udev_device);
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34       struct udev_device *udev_device_unref(struct udev_device *udev_device);
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DESCRIPTION

37       udev_device_new_from_syspath, udev_device_new_from_devnum,
38       udev_device_new_from_subsystem_sysname, udev_device_new_from_device_id,
39       and udev_device_new_from_environment allocate a new udev device object
40       and returns a pointer to it. This object is opaque and must not be
41       accessed by the caller via different means than functions provided by
42       libudev. Initially, the reference count of the device is 1. You can
43       acquire further references, and drop gained references via
44       udev_device_ref() and udev_device_unref(). Once the reference count
45       hits 0, the device object is destroyed and freed.
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47       udev_device_new_from_syspath, udev_device_new_from_devnum,
48       udev_device_new_from_subsystem_sysname, and
49       udev_device_new_from_device_id create the device object based on
50       information found in /sys, annotated with properties from the
51       udev-internal device database. A syspath is any subdirectory of /sys,
52       with the restriction that a subdirectory of /sys/devices (or a symlink
53       to one) represents a real device and as such must contain a uevent
54       file.  udev_device_new_from_devnum takes a device type, which can be b
55       for block devices or c for character devices, as well as a devnum (see
56       makedev(3)).  udev_device_new_from_subsystem_sysname looks up devices
57       based on the provided subsystem and sysname (see
58       udev_device_get_subsystem(3) and udev_device_get_sysname(3)) and
59       udev_device_new_from_device_id looks up devices based on the provided
60       device ID, which is a special string in one of the following four
61       forms:
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63       Table 1. Device ID strings
64       ┌──────────────┬──────────────────────────┐
65Example       Explanation              
66       ├──────────────┼──────────────────────────┤
67b8:2          │ block device major:minor │
68       ├──────────────┼──────────────────────────┤
69c128:1        │ char device major:minor  │
70       ├──────────────┼──────────────────────────┤
71n3            │ network device ifindex   │
72       ├──────────────┼──────────────────────────┤
73+sound:card29 │ kernel driver core       │
74       │              │ subsystem:device name    │
75       └──────────────┴──────────────────────────┘
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77       udev_device_new_from_environment creates a device from the current
78       environment (see environ(7)). Each key-value pair is interpreted in the
79       same way as if it was received in an uevent (see
80       udev_monitor_receive_device(3)). The keys DEVPATH, SUBSYSTEM, ACTION,
81       and SEQNUM are mandatory.
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RETURN VALUE

84       On success, udev_device_new_from_syspath(),
85       udev_device_new_from_devnum(),
86       udev_device_new_from_subsystem_sysname(),
87       udev_device_new_from_device_id() and udev_device_new_from_environment()
88       return a pointer to the allocated udev device. On failure, NULL is
89       returned, and errno is set appropriately.  udev_device_ref() returns
90       the argument that it was passed, unmodified.  udev_device_unref()
91       always returns NULL.
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SEE ALSO

94       udev_new(3), udev_device_get_syspath(3), udev_device_has_tag(3),
95       udev_enumerate_new(3), udev_monitor_new_from_netlink(3),
96       udev_list_entry(3), systemd(1),
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100systemd 241                                    UDEV_DEVICE_NEW_FROM_SYSPATH(3)
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