udev_device_new_from_syspath(3)

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
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SYNOPSIS

12       #include <libudev.h>
13
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(),
39       udev_device_new_from_device_id(), and
40       udev_device_new_from_environment() allocate a new udev device object
41       and returns a pointer to it. This object is opaque and must not be
42       accessed by the caller via different means than functions provided by
43       libudev. Initially, the reference count of the device is 1. You can
44       acquire further references, and drop gained references via
45       udev_device_ref() and udev_device_unref(). Once the reference count
46       hits 0, the device object is destroyed and freed.
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48       udev_device_new_from_syspath(), udev_device_new_from_devnum(),
49       udev_device_new_from_subsystem_sysname(), and
50       udev_device_new_from_device_id() create the device object based on
51       information found in /sys/, annotated with properties from the
52       udev-internal device database. A syspath is any subdirectory of /sys/,
53       with the restriction that a subdirectory of /sys/devices (or a symlink
54       to one) represents a real device and as such must contain a uevent
55       file.  udev_device_new_from_devnum() takes a device type, which can be
56       b for block devices or c for character devices, as well as a devnum
57       (see makedev(3)).  udev_device_new_from_subsystem_sysname() looks up
58       devices based on the provided subsystem and sysname (see
59       udev_device_get_subsystem(3) and udev_device_get_sysname(3)) and
60       udev_device_new_from_device_id() looks up devices based on the provided
61       device ID, which is a special string in one of the following four
62       forms:
63
64       Table 1. Device ID strings
65       ┌──────────────┬──────────────────────────┐
66       │Example       │ Explanation              │
67       ├──────────────┼──────────────────────────┤
68       │b8:2          │ block device major:minor │
69       ├──────────────┼──────────────────────────┤
70       │c128:1        │ char device major:minor  │
71       ├──────────────┼──────────────────────────┤
72       │n3            │ network device ifindex   │
73       ├──────────────┼──────────────────────────┤
74       │+sound:card29 │ kernel driver core       │
75       │              │ subsystem:device name    │
76       └──────────────┴──────────────────────────┘
77
78       udev_device_new_from_environment() creates a device from the current
79       environment (see environ(7)). Each key-value pair is interpreted in the
80       same way as if it was received in an uevent (see
81       udev_monitor_receive_device(3)). The keys DEVPATH, SUBSYSTEM, ACTION,
82       and SEQNUM are mandatory.
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RETURN VALUE

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

SYNOPSIS

DESCRIPTION

RETURN VALUE

SEE ALSO