Provided by: libsystemd-dev_255.4-1ubuntu8_amd64 
NAME
sd_session_is_active, sd_session_is_remote, sd_session_get_state, sd_session_get_uid,
sd_session_get_username, sd_session_get_seat, sd_session_get_start_time,
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, sd_session_get_leader - 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_username(const char *session, char **username);
int sd_session_get_seat(const char *session, char **seat);
int sd_session_get_start_time(const char *session, uint64_t *usec);
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_leader(const char *session, pid_t *leader);
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_username() may be used to determine the name of the Unix user the session
identified by the specified session identifier belongs to. The returned string needs to be
freed with the libc free(3) call after use.
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 (returning -ENODATA) for them. The returned string
needs to be freed with the libc free(3) call after use.
sd_session_get_start_time() may be used to determine the start time of the session
identified by the specified session identifier belongs to. The usec is in microseconds
since the epoch (CLOCK_REALTIME).
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_leader() may be used to determine the PID of the leader of the session
identified by the specified session identifier.
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_username(), sd_session_get_seat(), sd_session_get_service(),
sd_session_get_type(), sd_session_get_class(), sd_session_get_display(),
sd_session_get_leader(), 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
Functions described here are available as a shared library, which can be compiled against
and linked to with the libsystemd pkg-config(1) file.
The code described here uses getenv(3), which is declared to be not multi-thread-safe.
This means that the code calling the functions described here must not call setenv(3) from
a parallel thread. It is recommended to only do calls to setenv() from an early phase of
the program when no other threads have been started.
HISTORY
sd_session_get_state() was added in version 186.
sd_session_get_tty() was added in version 198.
sd_session_get_vt() was added in version 207.
sd_session_is_remote(), sd_session_get_remote_host(), and sd_session_get_remote_user()
were added in version 209.
sd_session_get_desktop() was added in version 217.
sd_session_get_username(), sd_session_get_start_time(), and sd_session_get_leader() were
added in version 254.
SEE ALSO
systemd(1), sd-login(3), sd_pid_get_session(3)
NOTES
1. Desktop Entry Specification
https://standards.freedesktop.org/desktop-entry-spec/latest/