sd_hwdb_new - Man Page

Create a new hwdb object and create or destroy references to it


#include <systemd/sd-hwdb.h>

int sd_hwdb_new(sd_hwdb **hwdb);

int sd_hwdb_new_from_path(const char *path, sd_hwdb **hwdb);

sd_hwdb* sd_hwdb_ref(sd_hwdb *hwdb);

sd_hwdb* sd_hwdb_unref(sd_hwdb *hwdb);


sd_hwdb_new() creates a new hwdb object to access the binary hwdb database. Upon initialization, the file containing the binary representation of the hardware database is located and opened. The new object is returned in hwdb.

sd_hwdb_new_from_path() may be used to specify the path from which the binary hardware database should be opened.

The hwdb object is reference counted. sd_hwdb_ref() and sd_hwdb_unref() may be used to get a new reference or destroy an existing reference to an object. The caller must dispose of the reference acquired with sd_hwdb_new() by calling sd_hwdb_unref() when done with the object.

Use sd_hwdb_seek(3), sd_hwdb_get(3), and sd_hwdb_enumerate(3) to access entries.

Return Value

On success, sd_hwdb_new() and sd_hwdb_new_from_path() return a non-negative integer. On failure, a negative errno-style error code is returned.

sd_hwdb_ref() always returns the argument.

sd_hwdb_unref() always returns NULL.


Returned errors may indicate the following problems:


The binary hardware database file could not be located. See systemd-hwdb(8) for more information.

Added in version 246.


The located binary hardware database file is in an incompatible format.

Added in version 246.


Memory allocation failed.

Added in version 246.


Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.


sd_hwdb_new(), sd_hwdb_ref(), and sd_hwdb_unref() were added in version 246.

sd_hwdb_new_from_path() was added in version 252.

See Also

systemd(1), systemd-udevd.service(8), sd-hwdb(3), systemd-hwdb(3)

Referenced By

sd-hwdb(3), sd_hwdb_get(3), systemd.directives(7), systemd.index(7).

The man pages sd_hwdb_new_from_path(3), sd_hwdb_ref(3) and sd_hwdb_unref(3) are aliases of sd_hwdb_new(3).

systemd 255