sd_pid_get_owner_uid, sd_pid_get_session, sd_pid_get_slice, sd_pid_get_user_slice, sd_pid_get_cgroup, sd_peer_get_owner_uid, sd_peer_get_session, 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
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_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_peer_get_owner_uid(int fd, uid_t *uid);
int sd_peer_get_session(int fd, char **session);
int sd_peer_get_slice(int fd, char **slice);
int sd_peer_get_user_slice(int fd, char **slice);
int sd_peer_get_cgroup(int fd, char **cgroup);
sd_pid_get_owner_uid() may be used to determine the Unix UID (user identifier) which owns the login session 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. 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_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 unified control group setup is used), or /sys/fs/cgroup/HIERARCHY/ (if the legacy multi-hierarchy control group setup is used).
If the pid parameter of any of these functions is passed as 0, the operation is executed for the calling process.
The sd_peer_get_owner_uid(), sd_peer_get_session(),
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.
On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code.
Returned errors may indicate the following problems:
These APIs are implemented as a shared library, which can be compiled and linked to with the libelogind pkg-config(1) file.
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).