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 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 free3 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 free3 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 free3 call after use. If the pid parameter of any of these functions is passed as 0 the operation is executed for the calling process. On success these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code. 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-config1 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 getsid2. systemd1, sd-login3, sd_session_is_active3, getsid2