# sd_varlink_send

## NAME



           sd_varlink_send, sd_varlink_sendb, sd_varlink_sendbo - Enqueues a
           Varlink method call, not expecting a reply
    


## SYNOPSIS



           **#include <systemd/sd-varlink.h>**
    
           **int sd_varlink_send(sd_varlink ***_link_**, const char ***_method_**,**
                               **sd_json_variant ***_parameters_**);**
    
           **int sd_varlink_sendb(sd_varlink ***_link_**, const char ***_method_**, ...);**
    
           **int sd_varlink_sendbo(sd_varlink ***_link_**, const char ***_method_**, ...);**
    


## DESCRIPTION



           **sd_varlink_send()** submits a method call via a Varlink connection.
           It takes the Varlink connection object, a method name as string
           parameter, and a JSON object containing the parameters to pass as
           function parameters. This call is asynchronous: the message will
           not be delivered immediately but only once **sd_varlink_process**(3)
           is invoked (which will happen automatically in one of the
           following event loop iterations if the Varlink connection is
           attached to an even loop).
    
           **sd_varlink_sendb()** is similar to **sd_varlink_send()** , but instead of
           expecting a fully constructed **sd_json_variant** object carrying the
           parameters, this object is constructed on-the-fly directly from
           the parameter list, in a style identical to **sd_json_build**(3).
    
           **sd_varlink_sendbo()** is identical to **sd_varlink_sendb()** , but an
           enclosing object is implicitly added, so that the parameter list
           is expected to consist of field pairs only. For details about the
           expected argument list, see **sd_json_buildo**(3).
    
           Use **sd_varlink_send()** , **sd_varlink_sendb()** and **sd_varlink_sendbo()**
           only if no method call results are required, as they neither
           provide return parameters nor success/failure information. Use
           **sd_varlink_call**(3) (and related calls) to submit a method call
           synchronously, returning the server's response.
    


## RETURN VALUE



           On success, **sd_varlink_send()** , **sd_varlink_sendb()** and
           **sd_varlink_sendbo()** return a non-negative integer. On failure,
           they return a negative errno-style error code.
    
       **Errors**
           Returned errors may indicate the following problems:
    
           **-EINVAL**
               An argument is invalid.
    
           **-ENOMEM**
               Memory allocation failed.
    
           **-ENOTCONN**
               The Varlink connection object is not connected.
    
           **-EBUSY**
               The Varlink connection object is already used for other
               purposes, i.e. executing a method call or similar.
    
           **-ENOBUFS**
               The internal limit of queued messages for the Varlink
               connection has been reached. This limit is set very high, and
               hitting it typically indicates that the Varlink connection
               object is stalled — possibly because **sd_varlink_process()** has
               not been called regularly enough, or because the peer is not
               processing any queued messages. This limit is a safety
               precaution to ensure a stalled peer will not result in
               unbounded memory allocations on the client side.
    


## 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.
    


* * *