systemd sd_device_enumerator_new 3 sd_device_enumerator_new sd_device_enumerator_ref sd_device_enumerator_unref sd_device_enumerator_unrefp Create, reference, and release a device enumerator object #include <systemd/sd-device.h> int sd_device_enumerator_new sd_device_enumerator **ret sd_device_enumerator* sd_device_enumerator_ref sd_device_enumerator *enumerator sd_device_enumerator* sd_device_enumerator_unref sd_device_enumerator *enumerator void sd_device_enumerator_unrefp sd_device_enumerator **enumerator The sd_device_enumerator family of functions provides a way to iterate over devices recognized by systemd-udevd8 . The enumerator allows filtering and matching devices by subsystem, properties and other attributes. sd_device_enumerator_new() creates a new device enumerator object and stores the result in the pointer referenced by ret. Returns 0 on success, or a negative errno-style error code on failure. sd_device_enumerator_ref() increases the reference count of the specified enumerator by one. sd_device_enumerator_unref() decreases the reference count of the enumerator by one. When the reference count reaches zero, the enumerator object is destroyed and cannot be used anymore, so further calls to sd_device_enumerator_unref() or sd_device_enumerator_unrefp() are illegal. sd_device_enumerator_unrefp() is similar to sd_device_enumerator_unref() but takes a pointer to a pointer to an sd_device_enumerator object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute. Note that this function is defined as an inline function. Use a declaration like the following, in order to allocate a sd_device_enumerator object that is freed automatically as the code block is left: { __attribute__((cleanup(sd_device_enumerator_unrefp))) sd_device_enumerator *enumerator = NULL; int r; … r = sd_device_enumerator_new(&enumerator); if (r < 0) fprintf(stderr, "Failed to allocate sd_device_enumerator: %s\n", strerror(-r)); … } sd_device_enumerator_ref() and sd_device_enumerator_unref() execute no operation if the enumerator is NULL. sd_device_enumerator_unrefp() will first dereference its argument, which must not be NULL, and will execute no operation if that is NULL. sd_device_enumerator_new() returns 0 on success or a negative errno-style error code on failure. sd_device_enumerator_ref() always returns the enumerator pointer. sd_device_enumerator_unref() always returns NULL. Returned errors may indicate the following problems: -ENOMEM Memory allocation failed. -EINVAL The argument is invalid. sd_device_enumerator_new(), sd_device_enumerator_ref(), sd_device_enumerator_unref(), and sd_device_enumerator_unrefp() were added in version 240. sd_device_ref3 sd_device_enumerator_add_match_parent 3