# TTY::Command [![Gitter](https://badges.gitter.im/Join%20Chat.svg)][gitter] [![Gem Version](https://badge.fury.io/rb/tty-command.svg)][gem] [![Build Status](https://secure.travis-ci.org/piotrmurach/tty-command.svg?branch=master)][travis] [![Build status](https://ci.appveyor.com/api/projects/status/0150ync7bdkfhmsv?svg=true)][appveyor] [![Code Climate](https://codeclimate.com/github/piotrmurach/tty-command/badges/gpa.svg)][codeclimate] [![Coverage Status](https://coveralls.io/repos/github/piotrmurach/tty-command/badge.svg)][coverage] [![Inline docs](http://inch-ci.org/github/piotrmurach/tty-command.svg?branch=master)][inchpages] [gitter]: https://gitter.im/piotrmurach/tty [gem]: http://badge.fury.io/rb/tty-command [travis]: http://travis-ci.org/piotrmurach/tty-command [appveyor]: https://ci.appveyor.com/project/piotrmurach/tty-command [codeclimate]: https://codeclimate.com/github/piotrmurach/tty-command [coverage]: https://coveralls.io/github/piotrmurach/tty-command [inchpages]: http://inch-ci.org/github/piotrmurach/tty-command > Run external commands with pretty output logging and capture stdout, stderr and exit status. Redirect stdin, stdout and stderr of each command to a file or a string. **TTY::Command** provides independent command execution component for [TTY](https://github.com/piotrmurach/tty) toolkit. ## Motivation Complex software projects aren't just a single app. These projects usually spawn dozens or hundreds of supplementary standalone scripts which are just as important as the app itself. Examples include - data validation, deployment, monitoring, database maintenance, backup & restore, configuration management, crawling, ETL, analytics, log file processing, custom reports, etc. One of the contributors to **TTY::Command** counted 222 scripts in the `bin` directory for his startup. Why should we be handcuffed to `sh` or `bash` for these scripts when we could be using Ruby? Ruby is easier to write and more fun, and we gain a lot by using a better language. It's nice for everyone to just use Ruby everywhere. **TTY::Command** tries to add value in other ways. It'll halt automatically if a command fails. It's easy to get verbose or quiet output as appropriate, or even capture output and parse it with Ruby. Escaping arguments is a breeze. These are all areas where traditional shell scripts tend to fall flat. ## Installation Add this line to your application's Gemfile: ```ruby gem "tty-command" ``` And then execute: $ bundle Or install it yourself as: $ gem install tty-command ## Contents * [1. Usage](#1-usage) * [2. Interface](#2-interface) * [2.1. Run](#21-run) * [2.2. Run!](#22-run) * [2.3. Logging](#23-logging) * [2.3.1. Color](#231-color) * [2.3.2. UUID](#232-uuid) * [2.3.3. Only output on error](#233-only-output-on-error) * [2.3.4. Verbose](#234-verbose) * [2.4. Dry run](#24-dry-run) * [2.5. Wait](#25-wait) * [2.6. Test](#26-test) * [2.7. Ruby interpreter](#27-ruby-interpreter) * [3. Advanced Interface](#3-advanced-interface) * [3.1. Environment variables](#31-environment-variables) * [3.2. Options](#32-options) * [3.2.1. Redirection](#321-redirection) * [3.2.2. Handling input](#322-handling-input) * [3.2.3. Timeout](#323-timeout) * [3.2.4. Binary mode](#324-binary-mode) * [3.2.5. Signal](#325-signal) * [3.2.6. PTY(pseudo-terminal)](#326-ptypseudo-terminal) * [3.2.7. Current directory](#327-current-directory) * [3.2.8. User](#328-user) * [3.2.9. Group](#329-group) * [3.2.10. Umask](#3210-umask) * [3.3. Result](#33-result) * [3.3.1. success?](#331-success) * [3.3.2. failure?](#332-failure) * [3.3.3. exited?](#333-exited) * [3.3.4. each](#334-each) * [3.4. Custom printer](#34-custom-printer) * [4. Example](#4-example) ## 1. Usage Create a command instance and then run some commands: ```ruby require "tty-command" cmd = TTY::Command.new cmd.run("ls -la") cmd.run("echo Hello!") ``` Note that `run` will throw an exception if the command fails. This is already an improvement over ordinary shell scripts, which just keep on going when things go bad. That usually makes things worse. You can use the return value to capture stdout and stderr: ```ruby out, err = cmd.run("cat ~/.bashrc | grep alias") ``` Instead of using a plain old string, you can break up the arguments and they'll get escaped if necessary: ```ruby path = "hello world" FileUtils.touch(path) cmd.run("sum #{path}") # this will fail due to bad escaping cmd.run("sum", path) # this gets escaped automatically ``` ## 2. Interface ### 2.1 Run Run starts the specified command and waits for it to complete. The argument signature of `run` is as follows: `run([env], command, [argv1, ...], [options])` The `env`, `command` and `options` arguments are described in the following sections. For example, to display file contents: ```ruby cmd.run("cat file.txt") ``` If the command succeeds, a `TTY::Command::Result` is returned that records stdout and stderr: ```ruby out, err = cmd.run("date") puts "The date is #{out}" # => "The date is Tue 10 May 2016 22:30:15 BST\n" ``` You can also pass a block that gets invoked anytime stdout and/or stderr receive output: ```ruby cmd.run("long running script") do |out, err| output << out if out errors << err if err end ``` If the command fails (with a non-zero exit code), a `TTY::Command::ExitError` is raised. The `ExitError` message will include: * the name of command executed * the exit status * stdout bytes * stderr bytes If the error output is very long, the stderr may contain only a prefix, number of omitted bytes and suffix. ### 2.2 Run! If you expect a command to fail occasionally, use `run!` instead. Then you can detect failures and respond appropriately. For example: ```ruby if cmd.run!("which xyzzy").failure? cmd.run("brew install xyzzy") end ``` ### 2.3 Logging By default, when a command is run, the command and the output are printed to `stdout` using the `:pretty` printer. If you wish to change printer you can do so by passing a `:printer` option: * `:null` - no output * `:pretty` - colorful output * `:progress` - minimal output with green dot for success and F for failure * `:quiet` - only output actual command stdout and stderr like so: ```ruby cmd = TTY::Command.new(printer: :progress) ``` By default the printers log to `stdout` but this can be changed by passing an object that responds to `<<` message: ```ruby logger = Logger.new("dev.log") cmd = TTY::Command.new(output: logger) ``` You can force the printer to always in print in color by passing the `:color` option: ```ruby cmd = TTY::Command.new(color: true) ``` If the default printers don't meet your needs you can always create [a custom printer](#34-custom-printer) #### 2.3.1 Color When using printers you can switch off coloring by using `:color` option set to `false`. #### 2.3.2 UUID By default, when logging is enabled and `pretty` printer is used, each log entry is prefixed by specific command run uuid number. This number can be switched off using the `:uuid` option at initialization: ```ruby cmd = TTY::Command.new(uuid: false) cmd.run("rm -R all_my_files") # => # Running rm -r all_my_files # ... # Finished in 6 seconds with exit status 0 (successful) ``` or individually per command run: ```rub cmd = TTY::Command.new cmd.run("echo hello", uuid: false) # => # Running echo hello # hello # Finished in 0.003 seconds with exit status 0 (successful) ``` #### 2.3.3 Only output on error When using a command that can fail, setting `:only_output_on_error` option to `true` hides the output if the command succeeds: ```ruby cmd = TTY::Command.new cmd.run("non_failing_command", only_output_on_error: true) ``` This will only print the `Running` and `Finished` lines, while: ```ruby cmd.run("non_failing_command") ``` will also print any output that the `non_failing_command` might generate. Running either: ```ruby cmd.run("failing_command", only_output_on_error: true) ``` either: ```ruby cmd.run("failing_command") ``` will also print the output. *Setting this option will cause the output to show at once, at the end of the command.* #### 2.3.4 Verbose By default commands will produce warnings when, for example `pty` option is not supported on a given platform. You can switch off such warnings with `:verbose` option set to `false`. ```ruby cmd.run("echo '\e[32mColors!\e[0m'", pty: true, verbose: false) ``` ### 2.4 Dry run Sometimes it can be useful to put your script into a "dry run" mode that prints commands without actually running them. To simulate execution of the command use the `:dry_run` option: ```ruby cmd = TTY::Command.new(dry_run: true) cmd.run(:rm, "all_my_files") # => [123abc] (dry run) rm all_my_files ``` To check what mode the command is in use the `dry_run?` query helper: ```ruby cmd.dry_run? # => true ``` ### 2.5 Wait If you need to wait for a long running script and stop it when a given pattern has been matched use `wait` like so: ```ruby cmd.wait "tail -f /var/log/production.log", /something happened/ ``` ### 2.6 Test To simulate classic bash test command you case use `test` method with expression to check as a first argument: ```ruby if cmd.test "-e /etc/passwd" puts "Sweet..." else puts "Ohh no! Where is it?" exit 1 end ``` ### 2.7 Ruby interpreter In order to run a command with Ruby interpreter do: ```ruby cmd.ruby %q{-e "puts 'Hello world'"} ``` ## 3. Advanced Interface ### 3.1 Environment variables The environment variables need to be provided as hash entries, that can be set directly as a first argument: ```ruby cmd.run({"RAILS_ENV" => "PRODUCTION"}, :rails, "server") ``` or as an option with `:env` key: ```ruby cmd.run(:rails, "server", env: {rails_env: :production}) ``` When a value in env is nil, the variable is unset in the child process: ```ruby cmd.run(:echo, "hello", env: {foo: "bar", baz: nil}) ``` ### 3.2 Options When a hash is given in the last argument (options), it allows to specify a current directory, umask, user, group and zero or more fd redirects for the child process. #### 3.2.1 Redirection There are few ways you can redirect commands output. You can directly use shell redirection like so: ```ruby out, err = cmd.run("ls 1&>2") puts err # => # CHANGELOG.md # CODE_OF_CONDUCT.md # Gemfile # ... ``` You can provide redirection as additional hash options where the key is one of `:in`, `:out`, `:err`, an integer (a file descriptor for the child process), an IO or array. For example, `stderr` can be merged into stdout as follows: ```ruby cmd.run(:ls, :err => :out) cmd.run(:ls, :stderr => :stdout) cmd.run(:ls, 2 => 1) cmd.run(:ls, STDERR => :out) cmd.run(:ls, STDERR => STDOUT) ``` The hash key and value specify a file descriptor in the child process (stderr & stdout in the examples). You can also redirect to a file: ```ruby cmd.run(:cat, :in => "file") cmd.run(:cat, :in => open("/etc/passwd")) cmd.run(:ls, :out => "log") cmd.run(:ls, :out => "/dev/null") cmd.run(:ls, :out => "out.log", :err => "err.log") cmd.run(:ls, [:out, :err] => "log") cmd.run("ls 1>&2", :err => "log") ``` It is possible to specify flags and permissions of file creation explicitly by passing an array value: ```ruby cmd.run(:ls, :out => ["log", "w"]) # 0664 assumed cmd.run(:ls, :out => ["log", "w", 0600]) cmd.run(:ls, :out => ["log", File::WRONLY|File::EXCL|File::CREAT, 0600]) ``` You can, for example, read data from one source and output to another: ```ruby cmd.run("cat", :in => "Gemfile", :out => "gemfile.log") ``` #### 3.2.2 Handling Input You can provide input to stdin stream using the `:input` key. For instance, given the following executable called `cli` that expects name from `stdin`: ```ruby name = $stdin.gets puts "Your name: #{name}" ``` In order to execute `cli` with name input do: ```ruby cmd.run("cli", input: "Piotr\n") # => Your name: Piotr ``` Alternatively, you can pass input via the :in option, by passing a `StringIO` Object. This object might have more than one line, if the executed command reads more than once from STDIN. Assume you have run a program, that first asks for your email address and then for a password: ```ruby in_stream = StringIO.new in_stream.puts "username@example.com" in_stream.puts "password" in_stream.rewind cmd.run("my_cli_program", "login", in: in_stream).out ``` #### 3.2.3 Timeout You can timeout command execution by providing the `:timeout` option in seconds: ```ruby cmd.run("while test 1; sleep 1; done", timeout: 5) ``` And to set it for all commands do: ```ruby cmd = TTY::Command.new(timeout: 5) ``` Please run `examples/timeout.rb` to see timeout in action. #### 3.2.4 Binary mode By default the standard input, output and error are non-binary. However, you can change to read and write in binary mode by using the `:binmode` option like so: ```ruby cmd.run("echo 'hello'", binmode: true) ``` To set all commands to be run in binary mode do: ```ruby cmd = TTY::Command.new(binmode: true) ``` #### 3.2.5 Signal You can specify process termination signal other than the default `SIGTERM`: ```ruby cmd.run("whilte test1; sleep1; done", timeout: 5, signal: :KILL) ``` #### 3.2.6 PTY(pseudo terminal) The `:pty` configuration option causes the command to be executed in subprocess where each stream is a `pseudo terminal`. By default this options is set to `false`. If you require to interface with interactive subprocess then setting this option to `true` will enable a `pty` terminal device. For example, a command may emit colored output only if it is running via terminal device. You may also wish to run a program that waits for user input, and simulates typing in commands and reading responses. This option will only work on systems that support BSD pty devices such as Linux or OS X, and it will gracefully fallback to non-pty device on all the other. In order to run command in `pseudo terminal`, either set the flag globally for all commands: ```ruby cmd = TTY::Command.new(pty: true) ``` or individually for each executed command: ```ruby cmd.run("echo 'hello'", pty: true) ``` Please note that setting `:pty` to `true` may change how the command behaves. It's important to understand the difference between `interactive` and `non-interactive` modes. For example, executing `git log` to view the commit history in default `non-interactive` mode: ```ruby cmd.run("git log") # => finishes and produces full output ``` However, in `interactive` mode with `pty` flag on: ```ruby cmd.run("git log", pty: true) # => uses pager and waits for user input (never returns) ``` In addition, when pty device is used, any input to command may be echoed to the standard output, as well as some redirects may not work. #### 3.2.7 Current directory To change directory in which the command is run pass the `:chdir` option: ```ruby cmd.run(:echo, "hello", chdir: "/var/tmp") ``` #### 3.2.8 User To run command as a given user do: ```ruby cmd.run(:echo, "hello", user: "piotr") ``` #### 3.2.9 Group To run command as part of group do: ```ruby cmd.run(:echo, "hello", group: "devs") ``` #### 3.2.10 Umask To run command with umask do: ```ruby cmd.run(:echo, "hello", umask: "007") ``` ### 3.3 Result Each time you run command the stdout and stderr are captured and return as result. The result can be examined directly by casting it to tuple: ```ruby out, err = cmd.run(:echo, "Hello") ``` However, if you want to you can defer reading: ```ruby result = cmd.run(:echo, "Hello") result.out result.err ``` #### 3.3.1 success? To check if command exited successfully use `success?`: ```ruby result = cmd.run(:echo, "Hello") result.success? # => true ``` #### 3.3.2 failure? To check if command exited unsuccessfully use `failure?` or `failed?`: ```ruby result = cmd.run(:echo, "Hello") result.failure? # => false result.failed? # => false ``` #### 3.3.3 exited? To check if command ran to completion use `exited?` or `complete?`: ```ruby result = cmd.run(:echo, "Hello") result.exited? # => true result.complete? # => true ``` #### 3.3.4 each The result itself is an enumerable and allows you to iterate over the stdout output: ```ruby result = cmd.run(:ls, "-1") result.each { |line| puts line } # => # CHANGELOG.md # CODE_OF_CONDUCT.md # Gemfile # Gemfile.lock # ... # lib # pkg # spec # tasks ``` By default the linefeed character `\n` is used as a delimiter but this can be changed either globally by calling `record_separator`: ```ruby TTY::Command.record_separator = "\n\r" ``` or configured per `each` call by passing delimiter as an argument: ```ruby cmd.run(:ls, "-1").each("\t") { ... } ``` ### 3.4 Custom printer If the built-in printers do not meet your requirements you can create your own. A printer is a regular Ruby class that can be registered through `:printer` option to receive notifications about received command data. As the command runs the custom printer will be notified when the command starts, when data is printed to stdout, when data is printed to stderr and when the command exits. Please see [lib/tty/command/printers/abstract.rb](https://github.com/piotrmurach/tty-command/blob/master/lib/tty/command/printers/abstract.rb) for a full set of methods that you can override. At the very minimum you need to specify the `write` method that will be called during the lifecycle of command execution. The `write` accepts two arguments, first the currently run command instance and second the message to be printed: ```ruby CustomPrinter < TTY::Command::Printers::Abstract def write(cmd, message) puts cmd.to_command + message end end cmd = TTY::Command.new(printer: CustomPrinter) ``` ## 4. Example Here's a slightly more elaborate example to illustrate how tty-command can improve on plain old shell scripts. This example installs a new version of Ruby on an Ubuntu machine. ```ruby cmd = TTY::Command.new # dependencies cmd.run "apt-get -y install build-essential checkinstall" # fetch ruby if necessary if !File.exists?("ruby-2.3.0.tar.gz") puts "Downloading..." cmd.run "wget http://ftp.ruby-lang.org/pub/ruby/2.3/ruby-2.3.0.tar.gz" cmd.run "tar xvzf ruby-2.3.0.tar.gz" end # now install Dir.chdir("ruby-2.3.0") do puts "Building..." cmd.run "./configure --prefix=/usr/local" cmd.run "make" end ``` ## Development After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment. ## Contributing Bug reports and pull requests are welcome on GitHub at https://github.com/piotrmurach/tty-command. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct. ## License The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT). ## Copyright Copyright (c) 2016 Piotr Murach. See LICENSE for further details.