NAME

       sd_bus_message_get_signature, sd_bus_message_is_empty, sd_bus_message_has_signature -
       Query bus message signature

SYNOPSIS

       #include <systemd/sd-bus.h>

       const char* sd_bus_message_get_signature(sd_bus_message *message, int complete);

       int sd_bus_message_is_empty(sd_bus_message *message);

       int sd_bus_message_has_signature(sd_bus_message *message, const char *signature);

DESCRIPTION

       sd_bus_message_get_signature() returns the signature of message message. If complete is
       true, the signature of the whole message is returned, and just the signature of the
       currently open container otherwise.

       sd_bus_message_is_empty() returns true if the message is empty, i.e. when its signature is
       empty.

       sd_bus_message_has_signature() returns true if the signature of the message message
       matches given signature. Parameter signature may be NULL, this is treated the same as an
       empty string, which is equivalent to calling sd_bus_message_is_empty().

RETURN VALUE

       On success, sd_bus_message_get_signature() returns the signature, and NULL on error.

       The other functions return 0 or a positive integer on success. On failure, they return a
       negative errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           The message parameter is NULL.

       NULL
           The message parameter is NULL.

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_bus_message_get_signature(), sd_bus_message_is_empty(), and
       sd_bus_message_has_signature() were added in version 240.

SEE ALSO

       systemd(1), sd-bus(3), sd_bus_message_new(3)