# sd_seat_get_active

## NAME



           sd_seat_get_active, sd_seat_get_sessions, sd_seat_can_tty,
           sd_seat_can_graphical - Determine state of a specific seat
    


## SYNOPSIS



           **#include <systemd/sd-login.h>**
    
           **int sd_seat_get_active(const char ***_seat_**, char ****_session_**,**
                                  **uid_t ***_uid_**);**
    
           **int sd_seat_get_sessions(const char ***_seat_**, char *****_ret_sessions_**,**
                                    **uid_t ****_ret_uids_**,**
                                    **unsigned int ***_ret_n_uids_**);**
    
           **int sd_seat_can_tty(const char ***_seat_**);**
    
           **int sd_seat_can_graphical(const char ***_seat_**);**
    


## DESCRIPTION



           **sd_seat_get_active()** may be used to determine which session is
           currently active on a seat, if there is any. Returns the session
           identifier and the user identifier of the Unix user the session is
           belonging to. Either the session or the user identifier parameter
           can be passed **NULL** , in case only one of the parameters shall be
           queried. The returned string needs to be freed with the libc
           free(3) call after use.
    
           **sd_seat_get_sessions()** may be used to determine all sessions on
           the specified seat. Returns two arrays, one (**NULL** terminated) with
           the session identifiers of the sessions and one with the user
           identifiers of the Unix users the sessions belong to. An
           additional parameter may be used to return the number of entries
           in the latter array. This value is the same as the return value if
           the return value is nonnegative. The output parameters may be
           passed as **NULL** in case these output values are not needed. The
           arrays and the strings referenced by them need to be freed with
           the libc free(3) call after use. Note that instead of an empty
           array **NULL** may be returned and should be considered equivalent to
           an empty array.
    
           **sd_seat_can_tty()** may be used to determine whether a specific seat
           provides TTY functionality, i.e. is useful as a text console.
    
           **sd_seat_can_graphical()** may be used to determine whether a
           specific seat provides graphics functionality, i.e. is useful as a
           graphics display.
    
           If the _seat_ parameter of any of these functions is passed as **NULL** ,
           the operation is executed for the seat of the session of the
           calling process, if there is any.
    


## RETURN VALUE



           On success, **sd_seat_get_active()** returns 0 or a positive integer.
           On success, **sd_seat_get_sessions()** returns the number of entries
           in the session identifier array. If the test succeeds,
           **sd_seat_can_tty()** and **sd_seat_can_graphical()** return a positive
           integer, if it fails 0. 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 seat.
    
           **-ENXIO**
               The specified seat is unknown.
    
           **-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.
    


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