Description¶

The sd_device_enumerator_add_match_parent() function adds a filter to the enumerator so that only devices under the tree of the specified parent device are enumerated. If this is called multiple times the previously set parent device is cleared and only the last call takes an effect.

The sd_device_enumerator_add_match_property() function adds a filter to the enumerator so that only devices with the specified property equals to the value are enumerated. Both property and value can be a glob pattern. When this is called multiple times, devices that have at least one of the specified properties with matching values are enumerated. That is, filters are ORed.

The sd_device_enumerator_add_match_property_required() function adds a filter to the enumerator so that only devices with the specified property equals to the value are enumerated. This function is similar to sd_device_enumerator_add_match_property(), but when this is called multiple times, devices that have all specified properties with matching values are enumerated. That is, filters are ANDed.

The sd_device_enumerator_add_match_subsystem() function adds a filter to the enumerator so that all devices in the specified subsystem, when match is true. When match is false, then all devices except those in the specified subsystem are enumerated. When called multiple times, positive filters are ORed, and negative ones are ANDed.

The sd_device_enumerator_add_match_sysattr() function adds a filter on the sysfs attribute sysattr matching value. value can be a glob pattern. If value is NULL, devices that either have (if match is true) or do not have (if match is false) the specified sysattr are included, regardless of its value. That is, NULL is mostly equivalent to "*". When this function is called multiple times, only devices that match all specified sysattr filters are enumerated. That is, these filters are ANDed.

The sd_device_enumerator_add_match_sysname() function adds a filter so that only devices whose sysname equals to sysname are enumerated. sysname can be a glob pattern. When called multiple times, filters are ORed.

The sd_device_enumerator_add_nomatch_sysname() function adds a filter so that devices whose sysname equals to sysname are excluded from the enumeration. This is useful for excluding specific devices from the enumeration process. When called multiple times, features are ANDed.

The sd_device_enumerator_add_match_tag() function adds a filter so that only devices tagged with tag are enumerated. When called multiple times, filters are ORed.

The sd_device_enumerator_allow_uninitialized() function allows devices that have not yet been initialized by udev to be included in the enumeration.

The sd_device_enumerator_add_all_parents() function enumerates all parent devices of the matching devices. This is useful for cases where you want to include all parent devices in the enumeration, such as when you are interested in the entire device tree leading up to a specific device.

Return Value¶

All functions return 0 or a positive integer on success, or a negative errno-style error code on failure.

Examples¶

/* SPDX-License-Identifier: MIT-0 */

#include <stdbool.h>
#include <stdio.h>
#include <systemd/sd-device.h>

int main(void) {
    __attribute__((cleanup(sd_device_enumerator_unrefp))) sd_device_enumerator *enumerator = NULL;
    sd_device *device;
    int r;

    /* Create a new device enumerator */
    r = sd_device_enumerator_new(&enumerator);
    if (r < 0) {
        fprintf(stderr, "Failed to create device enumerator: %s\n", strerror(-r));
        return 1;
    }

    /* Include only devices from the "usb" subsystem */
    r = sd_device_enumerator_add_match_subsystem(enumerator, "usb", true);
    if (r < 0) {
        fprintf(stderr, "Failed to add subsystem match: %s\n", strerror(-r));
        return 1;
    }

    /*
     * Exclude devices where the "removable" sysattr is "0"
     * These are typically non-removable devices like built-in USB interfaces
     */
    r = sd_device_enumerator_add_match_sysattr(enumerator, "removable", "0", false);
    if (r < 0) {
        fprintf(stderr, "Failed to add sysattr match: %s\n", strerror(-r));
        return 1;
    }

    /* Begin enumerating matching devices */
    for (device = sd_device_enumerator_get_device_first(enumerator);
         device;
         device = sd_device_enumerator_get_device_next(enumerator)) {
        const char *syspath;

        /* Get syspath for the device */
        if (sd_device_get_syspath(device, &syspath) >= 0)
            printf("Removable USB device found: %s\n", syspath);
    }
    return 0;
}

History¶

sd_device_enumerator_add_match_parent(), sd_device_enumerator_add_match_property(), sd_device_enumerator_add_match_subsystem(), sd_device_enumerator_add_match_sysattr(), sd_device_enumerator_add_match_sysname(), sd_device_enumerator_add_match_tag(), and sd_device_enumerator_allow_uninitialized() were added in version 240.

sd_device_enumerator_add_nomatch_sysname() was added in version 251.

sd_device_enumerator_add_match_property_required() was added in version 255.

sd_device_enumerator_add_all_parents() was added in version 258.

See Also¶

sd_device_ref(3), sd_device_enumerator_new(3), sd_device_enumerator_get_device_first(3)