systemd sd-varlink 3 sd-varlink APIs for Varlink IPC #include <systemd/sd-varlink.h> pkg-config --cflags --libs libsystemd sd-varlink.h is part of libsystemd3 and provides APIs for implementing Varlink IPC clients and services. See for more information about Varlink IPC. Varlink IPC uses JSON as marshalling format. The sd-varlink API relies on the sd-json3 API for JSON serialization, deserialization and manipulation. The varlinkctl1 tool makes the functionality implemented by sd-varlink available from the command line. systemd1 sd-event3 sd-json3 varlinkctl1 sd-bus3 pkg-config1