c++ - how to list USB mass storage devices programatically using libudev in Linux? -


i doing project mass storage devices in linux. trying write application list connected usb mass storage devices , give notification when new mass storage device plugged in. using libudev purpose. have used code found in "http://www.signal11.us/oss/udev/" . have done modification here 

  /* create list of devices in 'block' subsystem. */   enumerate = udev_enumerate_new(udev);   udev_enumerate_add_match_subsystem(enumerate, "block");   udev_enumerate_scan_devices(enumerate);   devices = udev_enumerate_get_list_entry(enumerate);

the problem list block devices. want usb mass storage devices. how list. 1 more problem how label of usb storage devices using libudev.

one solution match devices following criteria:

  • subsystem == "scsi", devtype == "scsi_device"
  • child device exists subsystem == "block"
  • child device exists subsystem == "scsi_disk"
  • parent device exists subsystem == "usb", devtype == "usb_device"

here example program (also available on github):

#include <libudev.h> #include <stdio.h>  static struct udev_device* get_child(      struct udev* udev, struct udev_device* parent, const char* subsystem) {   struct udev_device* child = null;   struct udev_enumerate *enumerate = udev_enumerate_new(udev);    udev_enumerate_add_match_parent(enumerate, parent);   udev_enumerate_add_match_subsystem(enumerate, subsystem);   udev_enumerate_scan_devices(enumerate);    struct udev_list_entry *devices = udev_enumerate_get_list_entry(enumerate);   struct udev_list_entry *entry;    udev_list_entry_foreach(entry, devices) {     const char *path = udev_list_entry_get_name(entry);     child = udev_device_new_from_syspath(udev, path);     break;   }    udev_enumerate_unref(enumerate);   return child; }  static void enumerate_usb_mass_storage(struct udev* udev) {   struct udev_enumerate* enumerate = udev_enumerate_new(udev);    udev_enumerate_add_match_subsystem(enumerate, "scsi");   udev_enumerate_add_match_property(enumerate, "devtype", "scsi_device");   udev_enumerate_scan_devices(enumerate);    struct udev_list_entry *devices = udev_enumerate_get_list_entry(enumerate);   struct udev_list_entry *entry;    udev_list_entry_foreach(entry, devices) {     const char* path = udev_list_entry_get_name(entry);     struct udev_device* scsi = udev_device_new_from_syspath(udev, path);      struct udev_device* block = get_child(udev, scsi, "block");     struct udev_device* scsi_disk = get_child(udev, scsi, "scsi_disk");      struct udev_device* usb       = udev_device_get_parent_with_subsystem_devtype(           scsi, "usb", "usb_device");      if (block && scsi_disk && usb) {         printf("block = %s, usb = %s:%s, scsi = %s\n",           udev_device_get_devnode(block),           udev_device_get_sysattr_value(usb, "idvendor"),           udev_device_get_sysattr_value(usb, "idproduct"),           udev_device_get_sysattr_value(scsi, "vendor"));     }      if (block)       udev_device_unref(block);      if (scsi_disk)       udev_device_unref(scsi_disk);      udev_device_unref(scsi);   }    udev_enumerate_unref(enumerate); }  int main() {   struct udev* udev = udev_new();    enumerate_usb_mass_storage(udev);    udev_unref(udev);   return 0; }

and it's output external disk:

block = /dev/sdb, usb = 0bc2:ab20, scsi = seagate

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