sd_pid_get_owner_uid

systemd

sd_pid_get_session

sd_pid_get_user_unit

sd_pid_get_unit

sd_pid_get_machine_name

sd_pid_get_slice

sd_pid_get_user_slice

sd_pid_get_cgroup

sd_pidfd_get_owner_uid

sd_pidfd_get_session

sd_pidfd_get_user_unit

sd_pidfd_get_unit

sd_pidfd_get_machine_name

sd_pidfd_get_slice

sd_pidfd_get_user_slice

sd_pidfd_get_cgroup

sd_peer_get_owner_uid

sd_peer_get_session

sd_peer_get_user_unit

sd_peer_get_unit

sd_peer_get_machine_name

sd_peer_get_slice

sd_peer_get_user_slice

sd_peer_get_cgroup

Determine the owner uid of the user unit or session, or the session, user unit, system unit, container/VM or slice that a specific PID or socket peer belongs to

#include <systemd/sd-login.h>

int

sd_pid_get_owner_uid

pid_t

pid

uid_t *

uid

int

sd_pid_get_session

pid_t

pid

char **

session

int

sd_pid_get_user_unit

pid_t

pid

char **

unit

int

sd_pid_get_unit

pid_t

pid

char **

unit

int

sd_pid_get_machine_name

pid_t

pid

char **

name

int

sd_pid_get_slice

pid_t

pid

char **

slice

int

sd_pid_get_user_slice

pid_t

pid

char **

slice

int

sd_pid_get_cgroup

pid_t

pid

char **

cgroup

int

sd_pidfd_get_owner_uid

int

pidfd

uid_t *

uid

int

sd_pidfd_get_session

int

pidfd

char **

session

int

sd_pidfd_get_user_unit

int

pidfd

char **

unit

int

sd_pidfd_get_unit

int

pidfd

char **

unit

int

sd_pidfd_get_machine_name

int

pidfd

char **

name

int

sd_pidfd_get_slice

int

pidfd

char **

slice

int

sd_pidfd_get_user_slice

int

pidfd

char **

slice

int

sd_pidfd_get_cgroup

int

pidfd

char **

cgroup

int

sd_peer_get_owner_uid

int

uid_t *

uid

int

sd_peer_get_session

int

char **

session

int

sd_peer_get_user_unit

int

char **

unit

int

sd_peer_get_unit

int

char **

unit

int

sd_peer_get_machine_name

int

char **

name

int

sd_peer_get_slice

int

char **

slice

int

sd_peer_get_user_slice

int

char **

slice

int

sd_peer_get_cgroup

int

char **

cgroup

Description

sd_pid_get_owner_uid() may be used to determine the Unix UID (user identifier) which owns the login session or systemd user unit of a process identified by the specified PID. For processes which are not part of a login session and not managed by a user manager, this function will fail with -ENODATA.

sd_pid_get_session() may be used to determine the login session identifier of a process identified by the specified process identifier. The session identifier is a short string, suitable for usage in file system paths. Please note the login session may be limited to a stub process or two. User processes may instead be started from their systemd user manager, e.g. GUI applications started using DBus activation, as well as service processes which are shared between multiple logins of the same user. For processes which are not part of a login session, this function will fail with -ENODATA. The returned string needs to be freed with the libc free(3) call after use.

sd_pid_get_user_unit() may be used to determine the systemd user unit (i.e. user service or scope unit) identifier of a process identified by the specified PID. The unit name is a short string, suitable for usage in file system paths. For processes which are not managed by a user manager, this function will fail with -ENODATA. The returned string needs to be freed with the libc free(3) call after use.

sd_pid_get_unit() may be used to determine the systemd system unit (i.e. system service or scope unit) identifier of a process identified by the specified PID. The unit name is a short string, suitable for usage in file system paths. Note that not all processes are part of a system unit/service. For processes not being part of a systemd system unit, this function will fail with -ENODATA. (More specifically, this call will not work for kernel threads.) The returned string needs to be freed with the libc free(3) call after use.

sd_pid_get_machine_name() may be used to determine the name of the VM or container is a member of. The machine name is a short string, suitable for usage in file system paths. The returned string needs to be freed with the libc free(3) call after use. For processes not part of a VM or container, this function fails with -ENODATA.

sd_pid_get_slice() may be used to determine the slice unit the process is a member of. See systemd.slice(5) for details about slices. The returned string needs to be freed with the libc free(3) call after use.

Similarly, sd_pid_get_user_slice() returns the user slice (as managed by the user's systemd instance) of a process.

sd_pid_get_cgroup() returns the control group path of the specified process, relative to the root of the hierarchy. Returns the path without trailing slash, except for processes located in the root control group, where "/" is returned. To find the actual control group path in the file system, the returned path needs to be prefixed with /sys/fs/cgroup/.

If the pid parameter of any of these functions is passed as 0, the operation is executed for the calling process.

The sd_pidfd_get_owner_uid(), sd_pidfd_get_session(), sd_pidfd_get_user_unit(), sd_pidfd_get_unit(), sd_pidfd_get_machine_name(), sd_pidfd_get_slice(), sd_pidfd_get_user_slice() and sd_pidfd_get_cgroup() calls operate similarly to their PID counterparts, but accept a PIDFD instead of a PID, which means they are not subject to recycle race conditions as the process is pinned by the file descriptor during the whole duration of the invocation. Note that these require a kernel that supports PIDFD. A suitable file descriptor may be acquired via pidfd_open(2).

The sd_peer_get_owner_uid(), sd_peer_get_session(), sd_peer_get_user_unit(), sd_peer_get_unit(), sd_peer_get_machine_name(), sd_peer_get_slice(), sd_peer_get_user_slice() and sd_peer_get_cgroup() calls operate similarly to their PID counterparts, but accept a connected AF_UNIX socket and retrieve information about the connected peer process. Note that these fields are retrieved via /proc/, and hence are not suitable for authorization purposes, as they are subject to races.

Return Value

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

Errors

Returned errors may indicate the following problems:

-ESRCH
The specified PID does not refer to a running process.

-EBADF
The specified file descriptor is invalid.

-ENODATA
The given field is not specified for the described process or peer.

-EINVAL
An input parameter was invalid (out of range, or NULL, where that is not accepted).

-ENOMEM
Memory allocation failed.

Notes

Note that the login session identifier as returned by sd_pid_get_session() is completely unrelated to the process session identifier as returned by getsid(2).

History

sd_peer_get_cgroup(), sd_peer_get_machine_name(), sd_peer_get_owner_uid(), sd_peer_get_session(), sd_peer_get_slice(), sd_peer_get_unit(), sd_peer_get_user_slice(), sd_peer_get_user_unit(), sd_pid_get_cgroup(), sd_pid_get_machine_name(), sd_pid_get_owner_uid(), sd_pid_get_session(), sd_pid_get_slice(), sd_pid_get_unit(), sd_pid_get_user_slice(), and sd_pid_get_user_unit() were added in version 236.

sd_pidfd_get_owner_uid(), sd_pidfd_get_session(), sd_pidfd_get_user_unit(), sd_pidfd_get_unit(), sd_pidfd_get_machine_name(), sd_pidfd_get_slice(), sd_pidfd_get_user_slice(), and sd_pidfd_get_cgroup() were added in version 253.