dofile

Dofile is a function in Lua's standard libraries that loads and executes a Lua source file. It reads the contents of the given file, compiles them into a chunk, and runs that chunk immediately. The function returns any values produced by the chunk’s return statement, or the last expression if there is no explicit return; if the chunk does not return a value, dofile yields no return value.

Signature and behavior: dofile([filename]) takes an optional filename. When a filename is provided, dofile searches for and opens that file to load and run it. If filename is nil or omitted, dofile reads a chunk from the standard input. If the file cannot be opened or the chunk contains an error, dofile raises an error rather than returning a value.

Environment and side effects: The executed chunk runs in the same global environment as the caller, so it can read and modify global variables and functions. dofile does not create or modify module-specific environments, and it does not cache the loaded file for future calls, unlike the require function.

Relation to loadfile and require: Dofile internally uses the mechanism of loadfile to obtain a chunk and then executes it. Unlike require, dofile does not insert the module into package.loaded, and it does not perform the module search path caching or versioning. If you need to inspect or control the chunk before execution, you can use loadfile and then call the resulting function, possibly within an error-protected wrapper.

Usage considerations: Common uses include running configuration or script files at runtime and reusing code without creating a formal module. Because dofile executes arbitrary code, it should be used only with trusted, verified files.