  The application of code clone technology accelerates code search, improves
code reuse efficiency, and assists in software quality assessment and code
vulnerability detection. However, the application of code clones also
introduces software quality issues and increases the cost of software
maintenance. As an important research field in software engineering, code clone
has been extensively explored and studied by researchers, and related studies
on various sub-research fields have emerged, including code clone detection,
code clone evolution, code clone analysis, etc. However, there lacks a
comprehensive exploration of the entire field of code clone, as well as an
analysis of the trend of each sub-research field. This paper collects related
work of code clones in the past ten years. In summary, the contributions of
this paper mainly include: (1) summarize and classify the sub-research fields
of code clone, and explore the relative popularity and relation of these
sub-research fields; (2) analyze the overall research trend of code clone and
each sub-research field; (3) compare and analyze the difference between academy
and industry regarding code clone research; (4) construct a network of
researchers, and excavate the major contributors in code clone research field;
(5) The list of popular conferences and journals was statistically analyzed.
The popular research directions in the future include clone visualization,
clone management, etc. For the clone detection technique, researchers can
optimize the scalability and execution efficiency of the method, targeting
particular clone detection tasks and contextual environments, or apply the
technology to other related research fields continuously.
