## Name

sd_pid_get_session, sd_pid_get_unit, sd_pid_get_owner_uid — Determine session, service or owner of a session of a specific PID

## Synopsis

    #include <systemd/sd-login.h>

`int sd_pid_get_session(` | pid_t pid,
| char** session`)`;

`int sd_pid_get_unit(` | pid_t pid,
| char** unit`)`;

`int sd_pid_get_owner_uid(` | pid_t pid,
| uid_t* uid`)`;

## Description

`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. Note that not all processes are part of a login session (e.g. system service processes, user processes that are shared between multiple sessions of the same user, or kernel threads). For processes not being part of a login session this function will fail. 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 unit (i.e. system service) identifier of a process identified by the specified process identifier. The unit name is a short string, suitable for usage in file system paths. Note that not all processes are part of a unit/service (e.g. user processes, or kernel threads). For processes not being part of a systemd unit/system service this function will fail. The returned string needs to be freed with the libc free(3) call after use.

`sd_pid_get_owner_uid()` may be used to determine the Unix user identifier of the owner of the session of a process identified the specified PID. Note that this function will succeed for user processes which are shared between multiple login sessions of the same user, where `sd_pid_get_session()` will fail. For processes not being part of a login session and not being a shared process of a user this function will fail.

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

## Return Value

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

## Notes

The `sd_pid_get_session()`, `sd_pid_get_pid()`, and `sd_pid_get_owner_uid()` interfaces are available as shared library, which can be compiled and linked to with the `libsystemd-login` 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).

## See Also

systemd(1), sd-login(7), sd_session_is_active(3), getsid(2)