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mojo run

Builds and executes a Mojo file.


mojo run [options] <path>


Compiles the Mojo file at the given path and immediately executes it. Another way to execute this command is to simply pass a file to mojo. For example:

mojo hello.mojo

Options for this command itself, such as the ones listed below, must appear before the input file path argument. Any command line arguments that appear after the Mojo source file path are interpreted as arguments for that Mojo program.


Compilation options

--no-optimization, -O0

Disables compiler optimizations. This might reduce the amount of time it takes to compile the Mojo source file. It might also reduce the runtime performance of the compiled executable.


Appends the given path to the list of directories to search for imported Mojo files.


Defines a named value that can be used from within the Mojo source file being executed. For example, -D foo=42 defines a name foo that, when queried with the sys.param_env module from within the Mojo program, would yield the compile-time value 42.

Target options

--target-triple <TRIPLE>

Sets the compilation target triple. Defaults to the host target.

--target-cpu <CPU>

Sets the compilation target CPU. Defaults to the host CPU.

--target-features <FEATURES>

Sets the compilation target CPU features. Defaults to the host features.


Sets the architecture for which to generate code.

--mcpu <CPU>

Sets the CPU for which to generate code.

--mtune <TUNE>

Sets the CPU for which to tune code.

Diagnostic options


Emits warnings for missing or partial docstrings.

--max-notes-per-diagnostic <INTEGER>

When the Mojo compiler emits diagnostics, it sometimes also prints notes with additional information. This option sets an upper threshold on the number of notes that can be printed with a diagnostic. If not specified, the default maximum is 10.

Experimental compilation options

--debug-level <LEVEL>

Sets the level of debug info to use at compilation. The value must be one of: none (the default value), line-tables, or full. Please note that there are issues when generating debug info for some Mojo programs that have yet to be addressed.

--sanitize <CHECK>

Turns on runtime checks. The following values are supported: address (detects memory issues), and thread (detects multi-threading issues). Please note that these checks are not currently supported when executing Mojo programs.

--debug-info-language <LANGUAGE>

Sets the language to emit as part of the debug info. The supported languages are: Mojo, and C. C is the default, and is useful to enable rudimentary debugging and binary introspection in tools that don't understand Mojo.

Common options

--help, -h

Displays help information.