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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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SD_HWDB_GET(3) sd_hwdb_get SD_HWDB_GET(3)
sd_hwdb_get, sd_hwdb_seek, sd_hwdb_enumerate,
SD_HWDB_FOREACH_PROPERTY - Seek to a location in hwdb or access
entries
#include <systemd/sd-hwdb.h>
int sd_hwdb_get(sd_hwdb *hwdb, const char *modalias,
const char *key, const char **value);
int sd_hwdb_seek(sd_hwdb *hwdb, const char *modalias);
int sd_hwdb_enumerate(sd_hwdb *hwdb, const char **key,
const char **value);
SD_HWDB_FOREACH_PROPERTY(hwdb, modalias, key, value);
sd_hwdb_get() queries the hwdb object created earlier with
sd_hwdb_new(3) for entries matching the specified string
modalias, and returns the value corresponding to the key key. The
value is returned as a NUL-terminated string in value. It must
not be modified by the caller and is valid as long as a reference
to hwdb is kept. When multiple patterns in the database match
modalias, the one with the highest priority is used. See hwdb(7)
for details.
sd_hwdb_seek() selects entries matching the specified string
modalias. Subsequent queries with sd_hwdb_enumerate() will access
the key-value pairs for that string.
sd_hwdb_enumerate() returns (in turn) all the key-value pairs
defined for the string used with sd_hwdb_seek(). Each pair is
returned as NUL-terminated strings in key and value. The strings
must not be modified by the caller and are valid as long as a
reference to hwdb is kept. When multiple patterns in the database
match modalias, the combination of all matching key-value pairs
is used. See hwdb(7) for details.
The SD_HWDB_FOREACH_PROPERTY() macro combines sd_hwdb_seek() and
sd_hwdb_enumerate(). No error handling is performed and iteration
simply stops on error. See the example below.
On success, sd_hwdb_get() and sd_hwdb_seek() return a
non-negative integer. On failure, they return a negative
errno-style error code.
sd_hwdb_enumerate() returns a positive integer if another
key-value pair was found or zero if all entries have already been
enumerated. On failure, it returns a negative errno-style error
code.
Errors
Returned errors may indicate the following problems:
-EINVAL
A parameter is NULL.
-ENOENT
An entry for the specified modalias was not found.
-EAGAIN
sd_hwdb_seek() was not called before sd_hwdb_enumerate().
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Example 1. Look up hwdb entries for a USB device
/* SPDX-License-Identifier: MIT-0 */
#include <stdio.h>
#include <stdint.h>
#include <sd-hwdb.h>
int print_usb_properties(uint16_t vid, uint16_t pid) {
char match[STRLEN("usb:vp") + DECIMAL_STR_MAX(uint16_t) * 2];
sd_hwdb *hwdb;
const char *key, *value;
int r;
/* Match this USB vendor and product ID combination */
xsprintf(match, "usb:v%04Xp%04X", vid, pid);
r = sd_hwdb_new(&hwdb);
if (r < 0)
return r;
SD_HWDB_FOREACH_PROPERTY(hwdb, match, key, value)
printf("%s: \"%s\" → \"%s\"\n", match, key, value);
sd_hwdb_unref(hwdb);
return 0;
}
int main(int argc, char **argv) {
print_usb_properties(0x046D, 0xC534);
return 0;
}
The effect is similar to calling systemd-hwdb query
usb:v046DpC534.
systemd(1), systemd-udevd.service(8), sd-hwdb(3), systemd-hwdb(8)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2022-12-17. (At that
time, the date of the most recent commit that was found in the
repository was 2022-12-16.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 252 SD_HWDB_GET(3)
Pages that refer to this page: sd-hwdb(3), sd_hwdb_new(3), systemd.directives(7), systemd.index(7)
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