Index · Directives systemd 254


sd_device_get_syspath, sd_device_get_devpath, sd_device_get_sysname, sd_device_get_sysnum, sd_device_get_subsystem, sd_device_get_devtype, sd_device_get_devname, sd_device_get_devnum, sd_device_get_ifindex, sd_device_get_driver, sd_device_get_diskseq — Returns various fields of device objects


#include <systemd/sd-device.h>
int sd_device_get_syspath(sd_device *device,
 const char **ret);
int sd_device_get_devpath(sd_device *device,
 const char **ret);
int sd_device_get_sysname(sd_device *device,
 const char **ret);
int sd_device_get_sysnum(sd_device *device,
 const char **ret);
int sd_device_get_subsystem(sd_device *device,
 const char **ret);
int sd_device_get_devtype(sd_device *device,
 const char **ret);
int sd_device_get_devname(sd_device *device,
 const char **ret);
int sd_device_get_devnum(sd_device *device,
 dev_t *ret);
int sd_device_get_ifindex(sd_device *device,
 int *ret);
int sd_device_get_driver(sd_device *device,
 const char **ret);
int sd_device_get_diskseq(sd_device *device,
 uint64_t *ret);


sd_device_get_syspath() returns the sysfs path of the specified device record, including the /sys prefix. Example: /sys/devices/virtual/tty/tty7

sd_device_get_devpath() returns the sysfs path of the specified device record, excluding the /sys prefix. Example: /devices/virtual/tty/tty7

sd_device_get_sysname() returns the sysfs name of the specified device record, i.e. the last component of the sysfs path. Example: "tty7" for the device /sys/devices/virtual/tty/tty7

sd_device_get_sysnum() returns the sysfs device number of the specified device record, i.e. the numeric suffix of the last component of the sysfs path. Example: "7" for the device /sys/devices/virtual/tty/tty7

sd_device_get_subsystem() returns the kernel subsystem of the specified device record. This is a short string fitting into a filename, and thus does not contain a slash and cannot be empty. Example: "tty", "block" or "net".

sd_device_get_devtype() returns the device type of the specified device record, if the subsystem manages multiple types of devices. Example: for devices of the "block" subsystem this can be "disk" or "partition"

sd_device_get_devname() returns the device node path of the specified device record if the device has a device node. Example: for /sys/devices/virtual/tty/tty7 the string /dev/tty7 is typically returned.

sd_device_get_devnum() returns the device node major/minor (i.e. dev_t) of the specified device record if the device has a device node (i.e. the one returned by sd_device_get_devname()). For devices belonging to the "block" subsystem this refers to a block device node, in all other cases to a character device node. Example: for the /sys/devices/virtual/tty/tty7 device this typically returns the device number with major/minor "4:7".

sd_device_get_ifindex() returns the network interface index of the specified device record, if the device encapsulates a network interface device, i.e. belongs to the "net" subsystem. Example: the "lo" interface typically has interface index 1.

sd_device_get_driver() returns the kernel driver name attached to the device. Note that the driver field is set on the devices consumed by the driver, not on the device created by it. Example: a PCI device /sys/bus/pci/devices/0000:00:1f.6 might be attached to a driver "e1000e".

sd_device_get_diskseq() returns the kernel disk sequence number of the block device. This number monotonically increases whenever a backing medium of a block device changes without the device name changing, and is relevant for block devices encapsulating devices with changing media (e.g. floppy or CD-ROM), or loopback block devices. Only defined for block devices, i.e. those of subsystem "block".

Return Value

On success, these calls return 0 or a positive integer. On failure, they return a negative errno-style error code.


Returned errors may indicate the following problems:


A specified parameter is invalid.


The requested field is not present in the device record.


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.

See Also