interpreter

interpreter is a minimal scripting language aimed at low-memory embedded systems.

Many other scripting languages currently exist for embedded use, including Lua, Tcl, and BASIC; however, their implementations require certain system calls (e.g. read()/write()) that may not be available or used on an embedded device. Additionally, their memory and/or non-volatile memory requirements may be too large for the targeted device. As a result, interpreter was made with the goal to allow advanced scripts to be run in minimal conditions. This included things like having only a few built-in functions, and only loading script from C-strings.

To use interpreter with your own device, you will need some malloc/free implementation and a freestanding standard library. Newlib can work well for this, although functions like atoi() and snprintf() will probably need to be rewritten (if you don't have an _sbrk defined).

interpreter features:

• Variable/function definition - in C and in script
• dynamic arrays
• if/else conditionals
• while loops
• a solve function to parse strings at script runtime

inconvenient features:

• some code formatting is enforced due to parser limitation
• all variables are global (i.e. scopes don't exist)
• whitespace is not always ignored

some TODO items:

• add better error messages
• better array support
• better string support
• for loops
• variable scopes

building and running

This project can be made for the host system (mv shell.c.bak shell.c; make) or an ARM system (mv shell.c shell.c.bak; make arm). Make's -j argument may be used to multithread compilation.

To run on the host system, run ./shell some_script_file. Note that IO functions are not built in, so you must define your own.
To use on an ARM device, simply link libinterp.a into your program and use the header files. See shell.c for an idea of how to the interpreter.

 

This project is still in heavy development, so don't expect too much. See the wiki for a scripting guide.