The Neotron Command Shell

Introduction

The Neotron Shell is the first application started by the OS. It allows the user to give the system commands, including:

Browsing filesystems on the SD card
Loading files from SD card into RAM
Inspecting the contents of RAM and ROM
Executing applications

The Shell uses the standard OS API and hence is much like a normal application. The only difference is that it uses a special region of memory, allowing it to remaining running whilst it loads another application into the main program area. Once that application is started, it can use the shell's memory region as it's own - the OS will re-initialise the shell when the application exits.

Analogies from the PC world would include MS-DOS's COMMAND.COM and CP/M's CCP, but at a functional level it's more like the U-Boot Shell.

Shell Expansion

Any argument of the form ${VAR} is replaced with the value stored in the environment variable called VAR.

Any argument containing a * character is taken to be a glob and is expanded to all the filenames matching that glob. Note that there are a limited number of arguments that can be given to a command, so attempts to glob more files than that number will generate an error.

Magic Devices

The OS supports a number of magic device filenames. The shell is unaware of this and just asks the OS to perform the specified operation on the given filenames.

Shell Commands

`DIR [/S] [<path>]`

Performs a directory listing, either for the current drive and directory or of the given absolute or relative path.

The /S option displays directories recursively.

`MKDIR [/P] <path>`

Creates a new directory, given either an absolute path or a relative path. Can optionally make all the intermediate paths too.

`TYPE <path>`

Displays the contents of a file, assuming it is ASCII text.

`HEXDUMP <path>`

Displays the contents of a file as hex encoded binary.

`COPY [/S] <source1> [<source2>...] <dest>`

Copies one or more files from one location to another. If one sourceX is specified dest can be a file or a directory. If multiple sourceX files are specified, dest must be a directory. The argument /S makes COPY look in subdirectories recursively.

`RENAME <old> <new>`

Changes the name of a file. Cannot move files between directories or drives.

`MOVE <src> <dest>`

Moves a file from one directory to another. The dest path can be on a different drive or in a different directory.

`DEL <path> [<path2>...]`

Deletes one or more files.

`RMDIR <path> [<path2>...]`

Deletes one or more empty directories.

`DELTREE <path> [<path2>...]`

Recursively deletes one or more directories.

`PEEK <addr>`

Displays the contents of ROM or RAM at the given address.

`POKE <addr> <value>`

Writes a new value to RAM at the given address. Attempts to write to ROM are ignored.

`SAVE <addr> <length> <file>`

Copies RAM or ROM to a file on disk.

`LOAD <path>`

Copies the contents of a file on disk to RAM.

`EXEC <path>`

Performs a LOAD of the given file, followed by a RUN. This command is implied if a command is given which matches the name of a file in the current directory, or in the system's PATH environment variable.

`RUN`

Runs a program already in memory (e.g. having used LOAD)

`SET <var> <value>`

Sets an environment variable to the given value. The value var should not include ${ or }.

$ SET PATH 0:/BIN;0:/OS/BIN

`ECHO <text>`

Prints some text to the console.

$ ECHO "Hello, world"

`LOADENV <path>`

Loads environment variables from a file.

$ LOADENV ./FILE.ENV

`SAVEENV <path>`

Saves environment variables to a file.

$ SAVEENV ./FILE.ENV

`SCRIPT <path>`

Runs the shell commands found in the given filename.

$ SCRIPT ./FILE.CMD

`EDIT <path>`

Starts a full-screen text editor.

$ EDIT 1:/README.TXT

$ # Set System, Hidden and Read Only, but clear Archive
$ ATTR /A- /S /H /R SYSTEM.DAT

Neotron - The Embedded Rust Home Computer Platform