sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions, sd_uid_get_seats, sd_uid_get_display — Determine login state of a specific Unix user ID
|const char *seat|
sd_uid_get_state() may be used to
determine the login state of a specific Unix user identifier. The
following states are currently known: "
(user not logged in at all), "
not logged in, but some user services running),
online" (user logged in, but not active, i.e.
has no session in the foreground), "
logged in, and has at least one active session, i.e. one session
in the foreground), "
closing" (user not logged
in, and not lingering, but some processes 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. The returned string needs to be freed with the
call after use.
sd_uid_is_on_seat() may be used to
determine whether a specific user is logged in or active on a
specific seat. Accepts a Unix user identifier and a seat
identifier string as parameters. The
require_active parameter is a boolean
value. If non-zero (true), this function will test if the user is
active (i.e. has a session that is in the foreground and accepting
user input) on the specified seat, otherwise (false) only if the
user is logged in (and possibly inactive) on the specified
sd_uid_get_sessions() may be used to
determine the current sessions of the specified user. Accepts a
Unix user identifier as parameter. The
require_active parameter controls whether
the returned list shall consist of only those sessions where the
user is currently active (> 0), where the user is currently
online but possibly inactive (= 0), or logged in at all but
possibly closing the session (< 0). The call returns a
NULL terminated string array of session
sessions which needs to be
freed by the caller with the libc
call after use, including all the strings referenced. If the
string array parameter is passed as
array will not be filled in, but the return code still indicates
the number of current sessions. Note that instead of an empty
NULL may be returned and should be
considered equivalent to an empty array.
sd_uid_get_seats() may be
used to determine the list of seats on which the user currently
has sessions. Similar semantics apply, however note that the user
may have multiple sessions on the same seat as well as sessions
with no attached seat and hence the number of entries in the
returned array may differ from the one returned by
sd_uid_get_display() returns the name
of the "primary" session of a user. If the user has graphical
sessions, it will be the oldest graphical session. Otherwise, it
will be the oldest open session.
sd_uid_get_state() returns 0 or a positive integer. If the test
sd_uid_is_on_seat() returns a positive integer; if it fails, 0.
sd_uid_get_seats() return the number
of entries in the returned arrays.
sd_uid_get_display() returns a non-negative code
on success. On failure, these calls return a negative errno-style error code.
Returned errors may indicate the following problems:
The given field is not specified for the described user.
The specified seat is unknown.
An input parameter was invalid (out of range, or NULL, where that is not
accepted). This is also returned if the passed user ID is
0xFFFFFFFF, which are undefined on Linux.
Memory allocation failed.
These APIs are implemented as a shared
library, which can be compiled and linked to with the