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 Determine session, service or owner of a session 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 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. 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(), and sd_pid_get_owner_uid() 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