Strictly speaking, NimScript is the subset of Nim that can be evaluated by Nim's builtin virtual machine (VM). This VM is used for Nim's compiletime function evaluation features, but also replaces Nim's existing configuration system.
So instead of a myproject.nim.cfg configuration file, you can use a myproject.nims file that simply contains Nim code controlling the compilation process. For a directory wide configuration, use config.nims instead of nim.cfg.
The VM cannot deal with importc, the FFI is not available, so there are not many stdlib modules that you can use with Nim's VM. However, at least the following modules are available:
The system module in NimScript mode additionally supports these operations: nimscript.
What is x.y.key = "value" in the configuration file becomes switch("x.y.key", "value"). --option is switch("option"). The system module also exports 2 -- templates for convenience:
--forceBuild # is the same as: switch("forceBuild")
The task template that the system module defines allows a NimScript file to be used as a build tool. The following example defines a task build that is an alias for the c command:
task build, "builds an example": setCommand "c"
In fact, as a convention the following tasks should be available:
Task | Description |
---|---|
build | Build the project with the required backend (c, cpp or js). |
tests | Runs the tests belonging to the project. |
bench | Runs benchmarks belonging to the project. |
If the task runs an external command via exec it should afterwards call setCommand "nop" to tell the Nim compiler that nothing else needs to be done:
task tests, "test regular expressions": exec "nim c -r tests" setCommand "nop"
Look at the module distros for some support of the OS's native package managers.
See the Nimble readme for more information.
NimScript can also be used directly as a portable replacement for Bash and Batch files. Use nim e myscript.nims to run myscript.nims. For example, installation of Nimble is done with this simple script:
mode = ScriptMode.Verbose var id = 0 while dirExists("nimble" & $id): inc id exec "git clone https://github.com/nim-lang/nimble.git nimble" & $id withDir "nimble" & $id & "/src": exec "nim c nimble" mvFile "nimble" & $id & "/src/nimble".toExe, "bin/nimble".toExe