sd_pid_get_session

systemd
Developer Lennart Poettering lennart@poettering.net
sd_pid_get_session 3
sd_pid_get_session sd_pid_get_unit sd_pid_get_user_unit sd_pid_get_owner_uid sd_pid_get_machine_name Determine session, service, owner of a session or container/VM of a specific PID

    #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_user_unit` pid_t pid char** unit int `sd_pid_get_owner_uid` pid_t pid uid_t* uid int `sd_pid_get_machine_name` pid_t pid char** name

## 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 system unit (i.e. system service) 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 (e.g. user processes, or kernel threads). For processes not being part of a systemd system unit this function will fail. (More specifically: this call will not work for processes that are part of user units, use `sd_pid_get_user_unit()` for that.) 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) identifier of a process identified by the specified PID. This is similar to `sd_pid_get_unit()` but applies to user units instead of system units.

`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.

`sd_pid_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.

If the `pid` parameter 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_unit()`, `sd_pid_get_user_unit()`, `sd_pid_get_owner_uid()` and `sd_pid_get_machine_name()` 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 3, sd_session_is_active 3, getsid 2