Frontends #

Joern contains multiple frontends, each responsible for parsing the source code and generating the AST for their respective language. X2CPG is the base on which all of the other frontends are built, and contains common structures by all of the languages. Each frontend contains the base arguments from x2cpg, as well as custom arguments that are frontend specific. See each respective languages’ page for a detailed explanation on what arguments are available and what each of the arguments do.

Invoking a specific frontend #

To generate the AST for for some program with a specific frontend, invoke the desired frontend from the joern-cli/frontends directory using the generated script. If the script is not there, make sure that Joern has been staged with sbt. As an example, to parse a given Python directory and generate an AST:

cd joern-cli/frontends/pysrc2cpg/
sbt scala stage
./pysrc2cpg /some/input/path --output someOutput --venvDir /some/venv/dir

The arguments given after the pysrc2cpg command can be a mixture of the args found in x2cpg, as well as the language specific args for Python.

If you would like to generate the full CPG for a given source directory, you can do so using the joern-parse command:

./joern-parse /some/input/path --language PYTHONSRC --frontend-args --venvDir /some/venv/dir

The language argument selects the frontend used to generate the AST. If this argument is omitted, joern-parse will select a frontend based on the supported file type with the largest number of files in the given input directory. The arguments passed after --frontend-args will be passed to the frontend that is being invoked.

Below is a list of each of the different frontends and the languages that they support: