NAME

       sd_session_is_active, sd_session_is_remote, sd_session_get_state, sd_session_get_uid,
       sd_session_get_seat, sd_session_get_service, sd_session_get_type, sd_session_get_class,
       sd_session_get_desktop, sd_session_get_display, sd_session_get_tty, sd_session_get_vt,
       sd_session_get_remote_host, sd_session_get_remote_user - Determine state of a specific
       session

SYNOPSIS

       #include <systemd/sd-login.h>

       int sd_session_is_active(const char *session);

       int sd_session_is_remote(const char *session);

       int sd_session_get_state(const char *session, char **state);

       int sd_session_get_uid(const char *session, uid_t *uid);

       int sd_session_get_seat(const char *session, char **seat);

       int sd_session_get_service(const char *session, char **service);

       int sd_session_get_type(const char *session, char **type);

       int sd_session_get_class(const char *session, char **class);

       int sd_session_get_desktop(const char *session, char **desktop);

       int sd_session_get_display(const char *session, char **display);

       int sd_session_get_remote_host(const char *session, char **remote_host);

       int sd_session_get_remote_user(const char *session, char **remote_user);

       int sd_session_get_tty(const char *session, char **tty);

       int sd_session_get_vt(const char *session, unsigned int *vt);

DESCRIPTION

       sd_session_is_active() may be used to determine whether the session identified by the
       specified session identifier is currently active (i.e. currently in the foreground and
       available for user input) or not.

       sd_session_is_remote() may be used to determine whether the session identified by the
       specified session identifier is a remote session (i.e. its remote host is known) or not.

       sd_session_get_state() may be used to determine the state of the session identified by the
       specified session identifier. The following states are currently known: "online" (session
       logged in, but session not active, i.e. not in the foreground), "active" (session logged
       in and active, i.e. in the foreground), "closing" (session nominally logged out, but some
       processes belonging to it are still around). In the future additional states might be
       defined, client code should be written to be robust in regards to additional state strings
       being returned. This function is a more generic version of sd_session_is_active(). The
       returned string needs to be freed with the libc free(3) call after use.

       sd_session_get_uid() may be used to determine the user identifier of the Unix user the
       session identified by the specified session identifier belongs to.

       sd_session_get_seat() may be used to determine the seat identifier of the seat the session
       identified by the specified session identifier belongs to. Note that not all sessions are
       attached to a seat, this call will fail for them. The returned string needs to be freed
       with the libc free(3) call after use.

       sd_session_get_service() may be used to determine the name of the service (as passed
       during PAM session setup) that registered the session identified by the specified session
       identifier. The returned string needs to be freed with the libc free(3) call after use.

       sd_session_get_type() may be used to determine the type of the session identified by the
       specified session identifier. The returned string is one of "x11", "wayland", "tty", "mir"
       or "unspecified" and needs to be freed with the libc free(3) call after use.

       sd_session_get_class() may be used to determine the class of the session identified by the
       specified session identifier. The returned string is one of "user", "greeter",
       "lock-screen", or "background" and needs to be freed with the libc free(3) call after use.

       sd_session_get_desktop() may be used to determine the brand of the desktop running on the
       session identified by the specified session identifier. This field can be set freely by
       desktop environments and does not follow any special formatting. However, desktops are
       strongly recommended to use the same identifiers and capitalization as for
       $XDG_CURRENT_DESKTOP, as defined by the Desktop Entry Specification[1]. The returned
       string needs to be freed with the libc free(3) call after use.

       sd_session_get_display() may be used to determine the X11 display of the session
       identified by the specified session identifier. The returned string needs to be freed with
       the libc free(3) call after use.

       sd_session_get_remote_host() may be used to determine the remote hostname of the session
       identified by the specified session identifier. The returned string needs to be freed with
       the libc free(3) call after use.

       sd_session_get_remote_user() may be used to determine the remote username of the session
       identified by the specified session identifier. The returned string needs to be freed with
       the libc free(3) call after use. Note that this value is rarely known to the system, and
       even then should not be relied on.

       sd_session_get_tty() may be used to determine the TTY device of the session identified by
       the specified session identifier. The returned string needs to be freed with the libc
       free(3) call after use.

       sd_session_get_vt() may be used to determine the VT number of the session identified by
       the specified session identifier. This function will return an error if the seat does not
       support VTs.

       If the session parameter of any of these functions is passed as NULL, the operation is
       executed for the session the calling process is a member of, if there is any.

RETURN VALUE

       If the test succeeds, sd_session_is_active() and sd_session_is_remote() return a positive
       integer; if it fails, 0. On success, sd_session_get_state(), sd_session_get_uid(),
       sd_session_get_seat(), sd_session_get_service(), sd_session_get_type(),
       sd_session_get_class(), sd_session_get_display(), sd_session_get_remote_user(),
       sd_session_get_remote_host() and sd_session_get_tty() return 0 or a positive integer. On
       failure, these calls return a negative errno-style error code.

ERRORS

       Returned errors may indicate the following problems:

       -ENXIO
           The specified session does not exist.

       -ENODATA
           The given field is not specified for the described session.

       -EINVAL
           An input parameter was invalid (out of range, or NULL, where that is not accepted).

       -ENOMEM
           Memory allocation failed.

NOTES

       The sd_session_is_active(), sd_session_get_state(), sd_session_get_uid(),
       sd_session_get_seat(), sd_session_get_service(), sd_session_get_type(),
       sd_session_get_class(), sd_session_get_display(), sd_session_get_remote_host(),
       sd_session_get_remote_user() and sd_session_get_tty() interfaces are available as a shared
       library, which can be compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO

       systemd(1), sd-login(3), sd_pid_get_session(3)

NOTES

        1. Desktop Entry Specification
           http://standards.freedesktop.org/desktop-entry-spec/latest/