# sd_uid_get_state

## NAME



           sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions,
           sd_uid_get_seats, sd_uid_get_display, sd_uid_get_login_time -
           Determine login state of a specific Unix user ID
    


## SYNOPSIS



           **#include <systemd/sd-login.h>**
    
           **int sd_uid_get_state(uid_t** _uid_**, char ****_state_**);**
    
           **int sd_uid_is_on_seat(uid_t** _uid_**, int** _require_active_**,**
                                 **const char ***_seat_**);**
    
           **int sd_uid_get_sessions(uid_t** _uid_**, int** _require_active_**,**
                                   **char *****_sessions_**);**
    
           **int sd_uid_get_seats(uid_t** _uid_**, int** _require_active_**,**
                                **char *****_seats_**);**
    
           **int sd_uid_get_display(uid_t** _uid_**, char ****_session_**);**
    
           **int sd_uid_get_login_time(uid_t** _uid_**, uint64_t ***_usec_**);**
    


## DESCRIPTION



           **sd_uid_get_state()** may be used to determine the login state of a
           specific Unix user identifier. The following states are currently
           known: "offline" (user not logged in at all), "lingering" (user
           not logged in, but some user services running), "online" (user
           logged in, but not active, i.e. has no session in the foreground),
           "active" (user 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
           libc free(3) 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 seat.
    
           **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 but possibly closing the
           session (< 0). The call returns a **NULL** terminated string array of
           session identifiers in _sessions_ which needs to be freed by the
           caller with the libc free(3) call after use, including all the
           strings referenced. If the string array parameter is passed as
           **NULL** , the array will not be filled in, but the return code still
           indicates the number of current sessions. Note that instead of an
           empty array **NULL** may be returned and should be considered
           equivalent to an empty array.
    
           Similarly, **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_sessions()**.
    
           **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_login_time()** may be used to determine the time the
           user's service manager has been invoked, which is the time when
           the user's first active session, since which they stayed logged in
           continuously, began. The _usec_ is in microseconds since the epoch
           (**CLOCK_REALTIME**). This call will fail with **-ENXIO** if the user is
           not currently logged in.
    


## RETURN VALUE



           On success, **sd_uid_get_state()** and **sd_uid_get_login_time()** returns
           0 or a positive integer. If the test succeeds, **sd_uid_is_on_seat()**
           returns a positive integer; if it fails, 0.  **sd_uid_get_sessions()**
           and **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.
    
       **Errors**
           Returned errors may indicate the following problems:
    
           **-ENODATA**
               The given field is not specified for the described user.
    
           **-ENXIO**
               The specified seat is unknown.
    
           **-EINVAL**
               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 **0xFFFF** or **0xFFFFFFFF** , which are undefined on Linux.
    
           **-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.
    


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