Command Parsing

How command parsing works

Once the GetLine() function gets your input, it attempts to split any command with the semicolon between them, like:

command1 arg1 arg2 ; command2 arg3 arg4

Any command that starts with either a space or a hashtag will be ignored as a comment, like: (Notice the extra space in the first comment)

 comment
#comment

The first word is a command, and all words following it in a single command text are the series of arguments. These words then get split to arguments (without the switch indicator -switch) and switches (arguments that come after the dash) using the ProvidedArgumentsInfo class, though it does much more than that.

This class contains these variables:

• Command: Target command

• ArgumentsText: Provided arguments and switches

• ArgumentsList: Array of arguments without the switches

• SwitchesList: Array of switches

• RequiredArgumentsProvided: Checks to see if the arguments are provided or not

• RequiredSwitchesProvided: Checks to see if the required switches are provided or not

• RequiredSwitchArgumentsProvided: Checks to see if the required switch arguments are provided or not

After the above class constructor is called, the shell attempts to execute a mod or alias command, if found. Else, the built-in command is going to be executed. It checks for these redirection flags:

• >>: Redirects the output to a file, overwriting the target file, such as command >> target.txt.

• >>>: Redirects the output to a file, appending to the target file, such as command >>> target.txt.

• |SILENT|: Redirects the output to a null console driver, which means no output, such as command |SILENT|.

If these flags are found, the shell sets the console driver as appropriate.

The shell then checks to see if the command is executable with the current user permissions. If the command is a strict command (CommandFlags.Strict) and the user has been granted either the administrator status or the PermissionTypes.RunStrictCommands permission, or if the command is not a strict command, then the shell is able to execute the specified command.

However, if the maintenance mode is on and the command is set not to run on maintenance mode (CommandFlags.NoMaintenance), then the shell bails from executing the command, with the message that it can't run in maintenance mode.

Finally, the command executor thread is fired up with the ExecuteCommandParameters instance to hold command execution parameters for the same thread. The thread is then started.

However, the command executor checks for these:

• If the provided command is a UESH script, the shell invokes a script executor.

• If the command is an external program found in the shell lookup path, which is usually $PATH, the shell attempts to scan these directories for the program and execute it.

• If the command is an internal command, it creates a separate thread for the command.

The ExecuteCommandWrapped() function allows you to execute a command in wrapped mode from your mod commands. However, your mods must execute a command that has one of the flags, called CommandFlags.Wrappable, otherwise, this function prints the list of wrappable commands.

Switch Management

You can know more about switch management by clicking on the below button:

Command Switch Management

Local Variables and Commands

Occasionally, you may run into conditions where you may have to set an environment variable locally before running a command. For example, on your Linux system, if you run a VNC server running on display :1 and you want to show a GUI application there from the terminal emulator, you'll have to run the command like this:

$ DISPLAY=:1 x_gui_app

The same thing can be done for local shell commands on Nitrocid, but the syntax is slightly different. You can assign local environment variables before running the command either by using the set command, which affects both the current and the future command runs, or you can limit it to just the command that you're going to run using the below syntax:

($env=value $env2="value with space") my_mod_command

Special characters

If a command, such as wrap, is set to use the arguments string, you can escape special characters that are defined by either the base Nitrocid regular expression driver, or by your custom regex driver. For example, if you want to pass a switch to a wrapped command, you can use the wrap command like this:

wrap help \-addon

Unknown characters will stay escaped, but that depends on the behavior of the regular expression driver.

-set switch property

Your commands can now change their behavior, depending on if the -set switch was passed to the command. You can use the parameters.SwitchSetPassed value just like below:

SetRange.cs

if (!parameters.SwitchSetPassed)
{
    TextWriters.Write(Translate.DoTranslation("You must pass the -set switch with the variable that you want to set this value to."), KernelColorType.Error);
    return KernelExceptionTools.GetErrorCode(KernelExceptionType.ShellOperation);
}