systemd Developer Lennart Poettering lennart@poettering.net sd_login_monitor_new 3 sd_login_monitor_new sd_login_monitor_unref sd_login_monitor_flush sd_login_monitor_get_fd sd_login_monitor_get_events sd_login_monitor Monitor login sessions, seats and users #include <systemd/sd-login.h> int sd_login_monitor_new const char* category sd_login_monitor** ret sd_login_monitor* sd_login_monitor_unref sd_login_monitor* m int sd_login_monitor_flush sd_login_monitor* m int sd_login_monitor_get_fd sd_login_monitor* m int sd_login_monitor_get_events sd_login_monitor* m sd_login_monitor_new() may be used to monitor login sessions, users and seats. Via a monitor object a file descriptor can be integrated into an application defined event loop which is woken up each time a user logs in, logs out or a seat is added or removed, or a session, user, or seat changes state otherwise. The first parameter takes a string which can be seat (to get only notifications about seats being added, removed or changed), session (to get only notifications about sessions being created or removed or changed) or uid (to get only notifications when a user changes state in respect to logins). If notifications shall be generated in all these conditions, NULL may be passed. Note that in the future additional categories may be defined. The second parameter returns a monitor object and needs to be freed with the sd_login_monitor_unref() call after use. sd_login_monitor_unref() may be used to destroy a monitor object. Note that this will invalidate any file descriptor returned by sd_login_monitor_get_fd(). sd_login_monitor_flush() may be used to reset the wakeup state of the monitor object. Whenever an event causes the monitor to wake up the event loop via the file descriptor this function needs to be called to reset the wake-up state. If this call is not invoked the file descriptor will immediately wake up the event loop again. sd_login_monitor_get_fd() may be used to retrieve the file descriptor of the monitor object that may be integrated in an application defined event loop, based around poll2 or a similar interface. The application should include the returned file descriptor as wake-up source for the events mask returned by sd_login_monitor_get_events(). Whenever a wake-up is triggered the file descriptor needs to be reset via sd_login_monitor_flush(). An application needs to reread the login state with a function like sd_get_seats3 or similar to determine what changed. sd_login_monitor_get_events() will return the poll() mask to wait for. This function will return a combination of POLLIN, POLLOUT and similar to fill into the .events field of struct pollfd. On success sd_login_monitor_new() and sd_login_monitor_flush() return 0 or a positive integer. On success sd_login_monitor_get_fd() returns a Unix file descriptor. On success sd_login_monitor_get_events() returns a combination of POLLIN, POLLOUT and suchlike. On failure, these calls return a negative errno-style error code. sd_login_monitor_unref() always returns NULL. The sd_login_monitor_new(), sd_login_monitor_unref(), sd_login_monitor_flush(), sd_login_monitor_get_fd() and sd_login_monitor_get_events() interfaces are available as shared library, which can be compiled and linked to with the libsystemd-login pkg-config1 file. systemd1, sd-login3, sd_get_seats3, poll2