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# MeTTa Execution Modes
[These are inherited from SWI-Prolog](https://www.swi-prolog.org/pldoc/man?section=cmdline)

MeTTa can be executed in one of the following modes:

- `mettalog [option ...] script-file [arg ...]`
Arguments after the script file are made available in the MeTTa flag `argv`.

- `mettalog [option ...] metta-file ... [[--] arg ...]`
This is the normal way to start MeTTa. The MeTTa flag `argv` provides access to `arg ...`. If the options are followed by one or more MeTTa file names (i.e., names with extension .metta), these files are loaded. The first file is registered in the MeTTa flag `associated_file`.

- `mettalog -o output -c metta-file ...`
The `-c` option is used to compile a set of MeTTa files into an executable.

- `mettalog -o output -b prolog-bootfile metta-file ...`
Bootstrap compilation.


### Command Line Options for Running MeTTa
[These are inherited from SWI-Prolog](https://www.swi-prolog.org/pldoc/man?section=cmdline)

Boolean options may be written as `--name` (true), `--noname` or `--no-name` (false).

- `--debug-on-interrupt`
Enable debugging on an interrupt signal immediately.

- `--home[=DIR]`
Use `DIR` as home directory.

- `--quiet`
Set the MeTTa flag `verbose` to `silent`, suppressing informational and banner messages. Also available as `-q`.

- `--no-debug`
Disable debugging.

- `--no-signals`
Inhibit any signal handling by MeTTa, a property that is sometimes desirable for embedded applications. This option sets the flag signals to false. Note that the handler to unblock system calls is still installed. This can be prevented using `--sigalert=0` additionally.

- `--no-threads`
Disable threading for the multi-threaded version at runtime. See also the flags `threads` and `gc_thread`.

- `--no-packs`
Do not attach extension packages (add-ons).

- `--no-pce`
Enable/disable the xpce GUI subsystem. Using `--pce` loads the xpce system in user space and `--no-pce` makes it unavailable in the session.

- `--on-error=style`
How to handle errors.

- `--on-warning=style`
How to handle warnings.

- `--pldoc[=port]`
Start the PlDoc documentation system on a free network port. If port is specified, the server is started at the given port and the browser is not launched.

- `--sigalert=NUM`
Use signal NUM (1 ... 31) for alerting a thread. If NUM is 0 (zero), this handler is not installed.

- `--no-tty`
Unix only. Switches controlling the terminal.

- `-O`
Optimised compilation.

- `-l file.metta`
Load file.metta.

- `-s file.metta`
Use file.metta as a script file.

- `-f file.metta`
Use file.metta as initialisation file instead of the default `init.metta`.

- `-F script`
Select a startup script from the MeTTa home directory.

- `-x prolog-bootfile`
Boot from prolog-bootfile instead of the system''s default boot file.

- `-p alias=path1[:path2 ...]`
Define a path alias for file_search_path.

- `--`
Stops scanning for more arguments.


### Controlling the Stack Sizes

```shell
$ mettalog --stack-limit=32g
```

- `--stack-limit=size[bkmg]`
Limit the combined size of the MeTTa stacks to the indicated size.

- `--table-space=size[bkmg]`
Limit for the table space.

- `--shared-table-space=size[bkmg]`
Limit for the table space for shared tables.

### Running Goals from the Command Line

- `-g goal`
Goal is executed just before entering the top level.

```shell
% mettalog <options> -g (go) -g (quit)
```

- `-t (goal)`
Use goal as an interactive top level instead of the default goal `!(repl!)`.

### Compilation Options
[MeTTa Code is tranliterated to SWI-Prolog code and compiled](https://www.swi-prolog.org/pldoc/man?section=runtime)

- `-c file.metta ...`
Compile files into an intermediate code file.

- `-o output`
Used in combination with `-c` to determine the output file for compilation.


### Informational Command Line Options

- `--arch`
When given as the only option, it prints the architecture identifier (see MeTTa flag `arch`) and exits. See also `--dump-runtime-variables`.

- `--dump-runtime-variables [=format]`
When given as the only option, it prints a sequence of variable settings that can be used in shell scripts to deal with MeTTa parameters.

```shell
eval `mettalog --dump-runtime-variables`
cc -I$PLBASE/include -L$PLBASE/lib/$PLARCH ...
```

- `--help`
When given as the only option, it summarises the most important options.

- `--version`
When given as the only option, it summarises the version and the architecture identifier.

- `--abi-version`
Print a key (string) that represents the binary compatibility on a number of aspects.


### Maintenance Options
[These are inherited from SWI-Prolog](https://www.swi-prolog.org/pldoc/man?section=cmdline)

- `-b initfile.metta ...-c file.metta ...`
Boot compilation.

- `-d token1,token2,...`
Print debug messages for DEBUG statements.