General information

Nish is a non-POSIX, multiplatform command-line shell currently in a beta stage. It offers some features common for commands' shells, like Tab completion, syntax highlighting, variables, aliases. But it doesn't provide, for example, own scripting language. More information about available features, you can find below. If you read this file on GitHub: please don't send pull requests here. All will be automatically closed. Any code propositions should go to the Fossil repository.

IMPORTANT: If you read the file in the project code repository: This version of the file is related to the future version of the shell. It may contain information not present in released versions of the program. For that information, please refer to the README.md file included into the release.

Features

Use database for store all data related to the shell

All the shell's data, configuration, history, variables and aliases are stored in SQLite database. It allows adding some interesting features to the shell, like searching through its history.

Global and local aliases

The shell allows declaring not only standard aliases, which are available everywhere, but also aliases which available only in the selected directories. For example, you can declare alias build which in one directory will be executing make -j5 and in another nim release. Aliases can be declared for just one directory or for each subdirectory of the selected directory too. At this moment, available options for aliases are:

• ID: The ID of the alias, used mostly for deleting or editing the selected alias.
• Name: The name of the alias. The text which have to be entered to execute the alias. It doesn't need to be unique, but if two aliases in the same directory have the same name, then the first one will be executed. The name can contain only letters, numbers, and underscores.
• Path: The main directory in which the alias works. It must be an existing directory.
• Recursive: If set to 1, the alias is available for all subdirectories of the path. If set to 0, is available only in the selected directory.
• Commands: The list of commands which will be executed as alias. The alias can execute a few commands, but then, each entry on the list have to be separated with new line.
• Description: The alias description. Showed on the aliases list.
• Output: Where to redirect the output of the commands executed by the alias. By default, or if this option set to stdout, the output not redirected at all. If set to stderr, then the standard output redirected to the standard error. When set to any other value, it is the path (relative or absolute) to the file to which the output will be saved. If the file exists, the output will be added to its content. IMPORTANT: only default setting allows interacting with the commands executed by the alias. Any other setting allows only read without any ability to pass any input to the executed commands.

For example, the definition of the alias can look that:

ID: 1
Name: mc
Path: /
Recursive: 1
Commands: mc --nosubshell
Description: Run MC without subshell
Output: stdout

The alias will be executed when the user enters mc in the shell. The alias is the global alias, it is available for the main directory / and all subdirectories. It executes command mc --nosubshell. The output of the alias will be as default, nothing is redirected.

The definition of the local alias can look that:

ID: 2
Name: listdocs
Path: /home/user
Recursive: 0
Commands: cd docs && ls -lh
Description: Enter docs directory and list all files
Output: result.txt

The alias will be executed when the user enters listdocs in the shell in the home directory. It doesn't work in any of its subdirectory. It enters docs directory and then runs the command ls -lh. If the next command should be executed only when the previous command was successful, use && to merge them. If the next command should be executed only when the previous failed, use || to merge them. The output of the alias will be redirected to the file result.txt which will be located in the same directory where the alias was executed.

You can also pass arguments to the commands of the alias. The substitutes for arguments are start with $ and have numbers from 1 to 9. Example: $1, $5. The definition of alias which uses arguments can look that:

ID: 3
Name: fossopen
Path: /home/user/Projects
Recursive: 0
Commands: fossil open fossil/$1.fossil --workdir $1
Description: Open fossil repo. Required parameter is the name of fossil repo.
Output: stderr

The alias will be executed when the user enters fossopen [reponame] in the shell. If the user enters only fossopen the shell will report a problem. The alias is the local alias, which means it doesn't work in subdirectories. It runs command fossil open fossil/[reponame].fossil --workdir [reponame]. For example, entering the shell's command: fossopen myrepo will execute command: fossil open fossil/myrepo.fossil --workdir myrepo. The output of the command will be redirected to the standard error.

There is also special argument $0 which mean all remaining arguments entered by the user. The definition of alias which uses that argument can look that:

ID: 4
Name: foss
Path: /
Recursive: 1
Commands: fossil $0
Description: Alias for command fossil.
Output: stdout

The alias will be executed when the user enters foss or foss [arguments] in the shell. For example, entering the shell's command: foss help will execute command: fossil help. The output of the alias will not be redirected.

Advanced shell's commands' history

There are available a few commands to manipulate the shell's commands' history like show history or clear it. It is also possible to set the amount of commands to store in the shell's history or the shell should store also invalid commands or not.

When there is some text entered by the user, the history search only commands which starts with the entered text.

The shell sorts the commands' history not only by most recently used but also by most frequently used. Additionally, the command allows selecting the amount of commands to show, their sorting order and criteria. These settings cam be set as permanent in the shell's options or ad hoc for the one time.

It is also possible to search for a command in the history with the separated shell command.

Advanced shell's configuration

All shell's options can be previewed from the shell. Additionally, it is possible to set them inside the shell and reset options' values to the default values. Also, there are options which are read-only, like for example, the current version of the shell's database schema.

Global and local environment variables

Beside standard support for environment variables, with set and unset commands, the shell also offers ability to set environment variables only for the selected directories, in the same way how aliases set. At this moment, available options for variables are:

• ID: The ID of the variable, used mostly for deleting or editing the selected variable
• Name: The name of the variable. It doesn't need to be unique, but if two variables in the same directory have the same name, then the last one value will be set as current value of the variable.
• Path: The main directory in which the variable set.
• Recursive: If set to 1, the variable is available for all subdirectories of the path. If set to 0, is available only in the selected directory.
• Type: The type of the variable's value. Determines what kind of values are acceptable for the variable. Currently, three types of variables are available. text: anything, number: any number, path: a valid path.
• Value: The value of the variable.
• Description: The variable description. Showed on the variables list.

For example, the definition of the variable can look that:

ID: 1
Name: MY_VAR
Path: /
Recursive: 1
Type: text
Value: someval
Description: Test variable

The definition of the local variable can look that:

ID: 2
Name: MY_VAR2
Path: /home/user
Recursive: 0
Type: number
Value: 12
Description: The second test variable

The variable will be available only in the user's home directory. It doesn't work in any of its subdirectory.

IMPORTANT: Commands set and unset doesn't work with the shell's specific environment variables presented above. They work only with the standard environment variables. To manage the shell's specific environment variables use subcommands of the variable command.

Setting the shell's prompt

The shell's prompt can be set to the output of the selected program or script. To do this, set the value of the shell's option promptCommand to the command line with the desired program or script and its arguments. For example, to set prompt to show the current date, use command options set promptCommand date. If you want to reset the prompt to the original state, reset its value with command options reset promptCommand.

ATTENTION: the command set as the shell's option promptCommand will be executed every time before you execute your command. Thus, be sure it isn't too heavy for your system, or it isn't dangerous, for example, it doesn't steal credentials, harm your system, etc.

Plugins

The shell's offers a very simple API which allows writing its plugins in any programming language. The communication between the shell and the plugin are made by standard input and output, where the API calls are sending as command line arguments. All arguments for the calls should be enclosed in quotes if they contain spaces. The plugin's system will probably change over time especially by adding new API calls. The plugins can reside in any location. The directory tools contains the example plugin testplugin.sh written in Bash.

The current version of API: 0.2 The minimum required version of API for plugins to work: 0.2

At this moment, available API calls from the shell:

• install: called during installation of the plugin (adding it to the shell).
• uninstall: called during removing of the plugin from the shell.
• enable: called during enabling the plugin.
• disable: called during disabling the plugin.
• init: called during initialization (starting) of the shell.
• info: called during showing information about the plugin. Requested response from the plugin should have form: answer [name of the plugin;description of the plugin;API version of the plugin;list of API used (separated by comma)]. This call is required for all plugins to work. If a plugin doesn't have it, it won't be added or enabled in the shell.
• preCommand [command]: called before the user's command will be executed. Command argument is the name of command and all its arguments entered by the user.
• postCommand [command]: called after the user's command execution. Command argument is the name of command and all its arguments entered by the user.
• [command] [arguments]: called when the plugin added the own or replaced one of the built-in commands. Command is the name of the command which will be executed, arguments are a string with arguments entered by the user.

ATTENTION: the calls set as the preCommand and postCommand will be executed every time before and after you execute your command. Thus, be sure it isn't too heavy for your system, or it isn't dangerous, for example, it doesn't steal credentials, harm your system, etc.

If the plugin doesn't answer on any API call from the shell, it should return error code 2, so the shell will known that the API's call isn't supported by the plugin.

Available API calls from plugins:

• showError [text]: show the text in the standard error output
• showOutput [text] ?color?: show the text in the standard output. The optional argument is the color of the message. Available options are: fgBlack, fgRed, fgGreen, fgYellow, fgBlue, fgMagenta, fgCyan, fgWhite and fgDefault
• setOption [option name] [option value] [option description] [option type]: set the shell's option. If the option doesn't exist, create a new with selected parameters. Option type should be one of: integer (positive and negative), float, boolean (true or false), historySort, natural (0 or above), text, command (the value will be checked if is a valid command before added)
• removeOption [option name]: remove the selected option from the shell.
• getOption [option name]: get the value of the selected shell's option.
• answer [text]: set the answer for the shell. At this moment, used only in info call from the shell.
• addCommand [command name] ?subcommand? ?subcommand? ...: add the new command to the shell. The name must be unique. The command will not be added if there is registered the shell's command with that name. If you want to replace an existing command, use call replaceCommand (see below). Commands named exit, set, unset and cd can't be added. Optional arguments subcommand are names of the command's subcommands used in the commands' completion system.
• deleteCommand [command name]: remove the selected command from the shell. The name must be a name of an existing shell's command.
• replaceCommand [command name]: replace the selected command with code from the plugin. The name must be a name of an existing shell's command.
• addHelp [topic] [usage] [help content]: add the new help entry to the shell. The topic must be unique. The help entry will not be added if there is one with that topic. If you want to replace an existing help entry, use call updateHelp (see below).
• deleteHelp [topic]: delete the help entry with the selected topic. The topic must be the topic of an existing help entry.
• updateHelp [topic] [usage] [help content]: update the existing help entry with the new values. The topic must be a topic of an existing help entry.

Advanced help system

The whole content of the help is added to the local database of the shell. It allows searching for help topics, but also to locally modify the help entries. The use can in any moment bring back the default content, or update the local with the new version, with the one command.

The content of the help is located in file help/help.cfg. Each entry has the following scheme:

[PluginPathOrModuleName]
topic="The help topic, used to show the help entry"
usage="The shell's command related to the help topic"
content="The content of the help entry"

The help system offers some basic text formatting features. Enclosing a text with some characters will change the color of the text. Most formatting works only in content setting.

• ? will change color to blue. Works in usage setting too. For example: ?all?
• [] will change color to cyan. Works in usage setting too. For example: [name]
• _ will change color to yellow. For example: _true_.
• ```` will change color to green. For example: command.

Tab completion

The shell offers the Tab completion for the user's entered commands with names of files and directories relative to the current directory and with available commands. It also allows selecting a completion from the list if there is more than one completion available.

It is possible to set the amount of the completions displayed on the list in the shell's options.

Additionally, the shell offers the Tab completion for arguments of commands. By default, the completion offers only names of directories and files as the completion. Changing its setting is possible in two ways:

1. Manually

   By using command completion add to add a new completion or completion edit [id] to edit an existing one, where ID is an ID of the completion to edit. You will be asked for several things during setting, like the name of the command and type of its parameters. It is possible to limit parameters only to directories or even disable the completion completely. If you select custom type of the completion, you will be also asked for the accepted values for the completion.

2. Importing from a file

   It is possible to import a completion from a file, previously generated with the command completion export [id] [filename] where filename is the name of the file to which the completion will be exported and ID is an ID of the completion to export. To import that completion, use the command completion import [filename] where filename is the name of the file to import.

Command completion export [id] [filename] exports the selected completion as a configuration file. It contains fields:

• Command: the command for which the completion is.
• Type: the type of completion. Can be: Directories only, Files only, Directories and files, Commands, Custom or Completion for the selected command should be disabled.
• Values: the values available for the completion. It is needed only for Custom type of the completion. All values must be separated by semicolon and in quotes.

For example, the file with an exported completion can look that:

Command=ls
Type=Custom
Values="te;ew;wr"

Command completion allows managing the Tab completions for commands, like deleting them, previewing or listing all of them. For more information about the command and its subcommands, please look at the corresponding shell's help entries.

Other features

• Coloring the user entered command on green when it is valid or red when it is invalid, separated colors for environment variables and commands' arguments which contains quotes or double quotes. Can be enabled or disabled in the shell's options.
• Suggestions for commands when the user entered an unknown command. It is possible to set the precision of the suggestions with the shell's option. The feature can be disabled either.
• Setting the terminal title, can be enabled or disabled in the shell's options.
• Theming system. It is possible to set the colors and style, like use underline, bold or italic font (if the terminal emulator supports it) for various of the shell's outputs (errors, help entries, etc.).
• Ability to execute command with or without the system's default shell. Additionally, the default behavior of the shell can be set in the shell's options.

How to install

Precompiled packages

There are available binary packages for Linux and FreeBSD 64-bit both on the download page. If you want to use Nish on different platform, you have to build it from the source.

Build from the source

You will need:

• Nim compiler
• Contracts
• Nimassets
• TermStyle
• Nancy
• Nimalyzer
• Norm
• Unittests2

You can install them manually or by using Nimble. In that second option, type nimble install https://github.com/thindil/nish to install the shell and all dependencies. Generally it is recommended to use nimble release to build the project in release (optimized) mode or nimble debug to build it in the debug mode.

Design goals

• Provide sane defaults: even if command shells are for power users, it doesn't mean that their time isn't valuable. Provide good default settings for the new installation of the shell.
• A simple, extendable core: the base shell should be small as possible, contains only things useful for everyone. The rest of functionality should be in the shell's plugins.
• Configure not rule: add an ability to configure, enable or disable almost everything: style, commands, functionality.
• Safety first: prioritize the safety and security over new features or even speed. A broken program is less useful than the working simple one.
• KISS: Keep It Simple Stupid: when looking for a solution of a problem, use the simplest approach. After all the code have been maintained for some time.

License

The project released under 3-Clause BSD license.

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That's all for now, as usual, I have probably forgotten about something important ;)

Bartek thindil Jasicki