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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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
#include <stdio.h>
#include <stdint.h>
#include <sd-hwdb.h>
int print_usb_properties(uint16_t vid, uint16_t pid) {
char match[15];
sd_hwdb *hwdb;
const char *key, *value;
int r;
/* Match this USB vendor and product ID combination */
snprintf(match, sizeof 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 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-11.) 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 246 SD_HWDB_GET(3)
Pages that refer to this page: sd_hwdb_new(3) , sd_hwdb_ref(3) , sd_hwdb_unref(3) , 30-systemd-environment-d-generator(7) , systemd.index(7)