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# mbland / go-script-bash

Framework for writing modular, discoverable, testable Bash scripts

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## The ./go script: a unified development environment interface

A ./go script aims to abstract away many of the steps needed to develop (and sometimes deploy) a software project. It is a replacement for READMEs and other documents that may become out-of-date, and when maintained properly, should provide a cohesive and discoverable interface for common project tasks.

For a five-minute overview of the framework, see Mike Bland's go-script-bash lightning talk at Surge 2016.

### Introduction

#### What's a ./go script?

The ./go script idea came from Pete Hodgson's blog posts In Praise of the ./go Script: Part I and Part II. To paraphrase Pete's original idea, rather than dump project setup, development, testing, and installation/deployment commands into a README that tends to get stale, or rely on oral tradition to transmit project maintenance knowledge, automate these tasks by encapsulating them all inside a single script in the root directory of your project source tree, conventionally named "go". Then the interface to these tasks becomes something like ./go setup, ./go test, and ./go deploy. Not only would this script save time for people already familiar with the project, but it smooths the learning curve, prevents common mistakes, and lowers friction for new contributors. This is as desirable a state for Open Source projects as it is for internal ones.

#### Is this related to the Go programming language?

No. The ./go script convention in general and this framework in particular are completely unrelated to the Go programming language. In fact, the actual ./go script can be named anything. However, the go command from the Go language distribution encapsulates many common project functions in a similar fashion.

#### Why write a framework?

Of course, the danger is that this ./go script may become as unwieldy as the README it's intended to replace, depending on the project's complexity. Even if it's heavily used and kept up-to-date, maintenance may become an intensive, frightening chore, especially if not covered by automated tests. Knowing what the script does, why it does it, and how to run it may become more and more challenging—resulting in the same friction, confusion, and fear the script was trying to avoid.

The ./go script framework makes it easy to provide a uniform and easy-to-use project maintenance interface that fits your project perfectly regardless of the mix of tools and languages, then it gets out of the way as fast as possible. The hope is that by making the right thing the easy thing, scripts using the framework will evolve and stay healthy along with the rest of your project sources, which makes everyone working with the code less frustrated and more productive all-around.

This framework accomplishes this by:

• encouraging modular, composable ./go commands implemented as individual scripts—in the language of your choice!
• providing a set of builtin utility commands and shell command aliases—see ./go help builtins and ./go help aliases
• supporting automatic tab-completion of commands and arguments through a lightweight API—see ./go help env and ./go help complete
• implementing a quick, flexible, robust, and convenient documentation system—document your script in the header, and help shows up automatically as ./go help my-command! See ./go help help.

Plus, its own tests serve as a model for testing command scripts of all shapes and sizes.

The inspiration for this model (and initial implementation hints) came from Sam Stephenson's rbenv Ruby version manager.

#### Why Bash?

It's the ultimate backstage pass! It's the default shell for most mainstream UNIX-based operating systems, easily installed on other UNIX-based operating systems, and is readily available even on Windows.

#### Will this work on Windows?

Yes. It is an explicit goal to make it as easy to use the framework on Windows as possible. Since Git for Windows in particular ships with Bash as part of its environment, and Bash is available within Windows 10 as part of the Windows Subsystem for Linux (Ubuntu on Windows), it's more likely than not that Bash is already available on a Windows developer's system. It's also available from the MSYS2 and Cygwin environments.

#### Why not use tool X instead?

Of course there are many common tools that may be used for managing project tasks. For example: Make, Rake, npm, Gulp, Grunt, Bazel, and the Go programming language's go tool. There are certainly more powerful scripting languages: Perl, Python, Ruby, and even Node.js is a possibility. There are even more powerful shells, such as the Z-Shell and the fish shell.

The ./go script framework isn't intended to replace all those other tools and languages, but to make it easier to use each of them for what they're good for. It makes it easier to write good, testable, maintainable, and extensible shell scripts so you don't have to push any of those other tools beyond their natural limits.

Bash scripting is really good for automating a lot of traditional command line tasks, and it can be pretty awkward to achieve the same effect using other tools—especially if your project uses a mix of languages, where using a tool common to one language environment to automate tasks in another can get weird. (Which is part of the reason why there are so many build tools tailored to different languages in the first place, to say nothing of the different languages themselves.)

If you want to incorporate different scripting languages or shells into your project maintenance, this framework makes it easy to do so. However, by starting with Bash, you can implement a ./go init command to check that these other languages or shells are installed and either install them automatically or prompt the user on how to do so. Since Bash is (almost certainly) already present, users can run your ./go script right away and get the setup or hints that they need, rather than wading through system requirements and documentation before being able to do anything.

Even if ./go init tells the user "go to this website and install this other thing", that's still an immediate, tactile experience that triggers a reward response and invites further exploration. (Think of Zork and the first "open mailbox" command.)

#### Where can I run it?

The real question is: Where can't you run it?

The core framework is written 100% in Bash and it's been tested under Bash 3.2, 4.2, 4.3, and 4.4 across OS X, Ubuntu Linux, Arch Linux, Alpine Linux, FreeBSD 9.3, FreeBSD 10.3, and Windows 10 (using all the environments described in the "Will this work on Windows?" section above).

#### Can I use it to write standalone programs that aren't project scripts?

Actually, yes. See the Standalone mode section below.

Also see the following question...

#### Can I have more than one ./go script in the same project source tree?

Yes. You can share one copy of the go-bash-framework sources, and even have common code in the lib/ directory, but set each script to use its own command scripts dir.

This may be especially useful if you're writing a standalone program, in which one script provides the actual program interface, and the other provides the development-only interface.

#### How is it tested?

The project's own ./go test command does it all. Combined with automatic tab-completion enabled by ./go env and pattern-matching via ./go glob, the ./go test command provides a convenient means of selecting subsets of test cases while focusing on a particular piece of behavior. (See ./go help test.)

The tests are written using mbland/bats, an optimized version of Sam Stephenson's Bash Automated Testing System (BATS). Code coverage comes from Simon Kagstrom's kcov code coverage tool, which not only provides code coverage for Bash scripts (!!!) but can push the results to Coveralls!

### Environment setup

To run a ./go script that uses this module, or to add it to your own project, you must have Bash version 3.2 or greater installed on your system. Run bash --version to make sure Bash is in your PATH and is a compatible version. You should see output like this:

GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15)
Copyright (C) 2007 Free Software Foundation, Inc.


If you do not see this, follow the instructions in the Installing Bash section later in this document.

Note: While Bash is required to run this framework, your individual command scripts can be in any other interpreted language installed on the host system.

### How to use this framework

First you'll need a copy of this framework available in your project sources. The most expedient way to bootstrap your program is to use the go-template file as a starting point (replacing curl with wget, fetch, or whichever tool you prefer):

$curl https://raw.githubusercontent.com/mbland/go-script-bash/master/go-template >./go$ chmod ugo+rx ./go

You may rename this file whatever you wish (i.e. it doesn't have to be named ./go), update its documentation and variables to fit your project, and check it into your project repository. See the go-template comments for details.

If you'd prefer to download a copy of the framework and check it into your sources, versioned archives are available from the go-script-bash Releases page. The archives for the current release are:

You can also add this repository to your project as a Git submodule:

$git submodule add https://github.com/mbland/go-script-bash <target-dir>$ git commit -m 'Add go-script-bash framework'
$git submodule update --init where <target-dir> is any point inside your project directory structure that you prefer. If you're not using go-template, create a bash script in the root directory of your project to act as the main ./go script. This script need not be named go, but it must contain the following lines, with @go "$@" as the last line of the script:

. "${0%/*}/go-core.bash" "scripts" @go "$@"

where:

• ${0%/*} produces the path to the project's root directory based on the path to the ./go script • ${0%/*}/go-core.bash produces the path to the framework's go-core.bash file within your project's copy of the framework (adjusted to reflect where your copy of go-script-bash actually resides)
• scripts is the path to the directory holding your project's command scripts relative to the project root (it can be any name you like)

#### Directory structure

The ./go script changes to the project root directory before executing any commands. That means every command script you write will also run within the project root directory, so every relative file and directory path will be interpreted as relative to the project root.

Your project structure may look something like this:

project-root/
go - main ./go script
lib/ - publicly-exported modules (if the project is a go-bash-script plugin)
scripts/ (or bin/) - project (or plugin) ./go command scripts
lib/ - project-specific Bash library modules (see "Modules" section)
plugins/ - (optional) third-party command scripts (see ./go help plugins)
.../
bin/ - plugin ./go command scripts
lib/ - publicly-exported Bash library modules (see "Modules" section)
go-script-bash/
go-core.bash - top-level functions
lib/ - publicly-exported Bash library modules (see "Modules" section)
libexec/ - builtin ./go command scripts


This structure implies that the first line of your ./go script will be:

. "${0%/*}/scripts/go-script-bash/go-core.bash" "scripts" #### Variables and plugin scoping The following variables are set by the framework based on the above example (note there are many other variables set in go-core.bash and elsewhere; see ./go help vars): • _GO_ROOTDIR: /absolute/path/to/project-root • _GO_CORE_DIR: /absolute/path/to/project-root/scripts/go-script-bash • _GO_SCRIPTS_DIR: $_GO_ROOTDIR/scripts
• _GO_PLUGINS_DIR: /absolute/path/to/project-root/plugins

For plugins, _GO_ROOTDIR and _GO_SCRIPTS_DIR will be scoped to the root directory of the plugin installation; the other variables will remain the same. See ./go help plugins for more details.

#### Command scripts

Each command script for your project residing in the scripts directory must adhere to the following conditions:

• No filename extensions.
• It must be executable, with a #! (a.k.a. "she-bang") line. The interpreter name will be parsed from this line, whether it is an absolute path (#!/bin/bash) or is of the form: #!/usr/bin/env bash.
• If scripts/parent is a command script, subcommand scripts must reside within a directory named: scripts/parent.d.

Scripts can use any interpreted language available on the host system; they need not be written in Bash. Bash scripts will be sourced (i.e. imported into the same process running the ./go script itself). Other languages will use the PATH environment variable to discover the interpreter for the script.

See ./go help commands for details on the algorithm used to discover command scripts for execution.

#### Command summaries and help text

The builtin ./go help command will parse command script summaries and help text from the header comment block of each script. Run ./go help help to learn more about the formatting rules.

#### Tab completion

By evaluating the value of ./go env - within your shell, all builtin commands and aliases provide automatic tab completion of file, directory, and other arguments. If an implementation isn't available for your shell (within lib/internal/env/), it's very easy to add one. Feel free to open an issue or, better yet, send a pull request!

To learn the API for adding tab completion to your own command scripts, run ./go help complete. You can also learn by reading the scripts for the builtin commands.

#### Standalone mode

If you wish to use the framework to write a standalone program, rather than a project-specific development script, set _GO_STANDALONE in your top-level script to prevent alias commands, builtin commands, and plugin commands from showing up in help output or from being offered as tab completions. (help will still appear as a top-level tab completion.) All of these commands will still be available, but users won't be presented with them directly.

_GO_STANDALONE also prevents the script from setting PWD to _GO_ROOTDIR, enabling the script to process relative file path arguments anywhere in the file system. Note that then you'll have to add _GO_ROOTDIR manually to any _GO_ROOTDIR-relative paths in your own scripts.

#### Including common code

There are a number of possible methods available for sharing code between command scripts. Some possibilities are:

• The generally preferred method is to use . $_GO_USE_MODULES to source optional library modules; see the Modules section. • Include common code and constants in the top-level ./go script, after sourcing go-core.bash and before calling @go. • Source a file in the same directory that isn't executable. • Source a file in a child directory that may not have a name of the form: parent.d. • Source files from a dedicated directory relative to $_GO_ROOTDIR, e.g.:
. "path/to/lib/common.sh"
• Subcommand scripts can source the parent command via:
. "${BASH_SOURCE[0]%.d/*}" #### Command script API Any script in any language can invoke other command scripts by running ./go <command> [args..]. In Bash, however, you can also invoke the @go function directly as @go <command> [args...]. The @go, @go.printf, and @go.print_stack_trace functions are available to command scripts written in Bash, as Bash command scripts are sourced rather than run using another language interpreter. A number of global variables defined and documented in go-core.bash, all starting with the prefix _GO_, are exported as environment variables and available to scripts in all languages (along with the global COLUMNS environment variable). Run ./go vars to see them all along with their values, and run ./go help vars for more details. #### Plugins You can add third-party plugin command scripts to the plugins subdirectory of your scripts directory. Run ./go help plugins for more information. #### Modules You can import optional Bash library code from the core framework, third-party plugins, or your own project's scripts directory by sourcing the _GO_USE_MODULES script. For example, to import the core logging utilities: . "$_GO_USE_MODULES" 'log'

Run ./go help modules and ./go modules --help for more information.

#### Logging

The core library log module provides functions for standard logging facilities. For example:

@go.log INFO Hello, World!
@go.log ERROR Goodbye, World!

For more information, run ./go modules --help log.

#### Bats test assertions and helpers

The assertions and helpers from the test suite have been extracted into the lib/bats libraries. While these are not modules you can import with _GO_USE_MODULES, they are completely independent of the rest of the core framework and you may source them in your own Bats tests. (Whether or not these will ever become a separate library remains an open question.)

Variables, helper functions, and assertions for testing features based on the core framework are available in the lib/testing directory. The lib/bats-main library makes it easy to write a ./go test command script with the same interface and features as the core framework's ./go test command.

#### kcov-ubuntu module for test coverage on Linux

The kcov-ubuntu module provides the run_kcov function that will download and compile kcov, then run kcov with the original ./go command line arguments to collect test coverage. Only available on Ubuntu Linux for now, hence the name. Run ./go modules --help kcov-ubuntu for more information and see scripts/test for an example of how it may be used.

### Feedback and contributions

Feel free to comment on or file a new GitHub issue or otherwise ping @mbland with any questions or comments you may have, especially if the current documentation hasn't addressed your needs.

If you'd care to contribute to this project, be it code fixes, documentation updates, or new features, please read the CONTRIBUTING file.

### Installing Bash

If you're using a flavor of UNIX (e.g. Linux, OS X), you likely already have a suitable version of Bash already installed and available. If not, use your system's package manager to install it.

On Windows, the Git for Windows, MSYS2 and Cygwin distributions all ship with a version of Bash. On Windows 10, you can also use the Windows Subsystem for Linux.

#### Updating your PATH environment variable

Once you've installed bash, your PATH environment variable must include its installation directory. On UNIX, you can add it in the appropriate initialization file for your shell; look up your shell documentation for details.

On Windows, in most cases, you'll use the terminal program that ships with Git for Windows, MSYS2, or Cygwin, or you'll invoke the Windows System for Linux environment by entering bash in a built-in Command Prompt window. These terminals automatically set PATH so that Bash is available.

However, if you want to use the Git, MSYS2, or Cygwin bash from the built-in Command Prompt window, open the Start menu and navigate to Windows System > Control Panel > System and Security > System > Advanced system settings. Click the Environment Variables... button, select PATH, and add the directory containing your bash installation. The likely paths for each environment are:

• Git: C:\Program Files\Git\usr\bin\
• MSYS2: C:\msys64\usr\bin\
• Cygwin: C:\cygwin64\bin\

To use one of these paths temporarily within a Command Prompt window, you can run the following:

C:\path\to\my\go-script-bash> set PATH=C:\Program Files\Git\usr\bin\;%PATH%

# To verify:
C:\path\to\my\go-script-bash> echo %PATH%
C:\path\to\my\go-script-bash> where bash

# To run the tests:
C:\path\to\my\go-script-bash> bash ./go test


It should not be necessary to set Bash as your default shell. On Windows, however, you may wish to execute the bash command to run it as your shell before executing the ./go script or any other Bash scripts, to avoid having to run it as bash ./go every time.

#### Recommended utilities

Most of the framework as-is does not require any other external tools. However, in order for the automatic command help and output formatting to work, you'll need the following utilities installed:

• tput (ncurses) on Linux, OS X, UNIX
• mode.com should be present on Windows

To use the get file builtin, either curl, wget, or fetch must be installed on your system. get git-repo requires git, naturally.

This software is made available as Open Source software under the ISC License. For the text of the license, see the LICENSE file.

### Prior work

This is a Bash-based alternative to the 18F/go_script Ruby implementation.

Framework for writing modular, discoverable, testable Bash scripts

## Releases 11

go-script-bash v1.7.0 Latest
Oct 8, 2017

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