shelldoc: Test Unix shell commands in Markdown documentation

Markdown is widely used for documentation and README.md files that explain how to use or build some software. Such documentation often contains shell commands that explain how to build a software or how to run it. To make sure the documentation is accurate and up-to-date, it should be automatically tested. shelldoc tests Unix shell commands in Markdown files and reports the results.

Basic usage

shelldoc parses a Markdown input file, detects the code blocks in it, executes them and compares their output with the content of the code block. For example, the following code block contains a command, indicated by either leading a $ or a > trigger character, and an expected response:

$ echo Hello
Hello

Lines in code blocks that begin with a $ or a > trigger character are considered commands. Lines inbetween without those lead characters are considered the expected response. shelldoc will execute these commands and return whether or not the commands succeeded and the output matches the specificaton:

% shelldoc README.md 
SHELLDOC: doc-testing "go/src/github.com/endocode/shelldoc/README.md" ...
 CMD (1): echo Hello                                ?  Hello                      :  PASS (match)
 CMD (2): go get -u github.com/endocode/shelldo...  ?  ...                        :  PASS (match)
 CMD (3): export GREETING="Hello World"             ?  (no response expected)     :  PASS (execution successful)
 CMD (4): echo $GREETING                            ?  Hello World                :  PASS (match)
SUCCESS: 4 tests (4 successful, 0 failures, 0 execution errors)

Note that this example is not executed as a test by shelldoc, since it does not start with a trigger character. Trying to do so would cause an infinite recursion when evaluating the README.md using shelldoc. Try it :-) The percent symbol is commonly used as a shell prompt next to $ or a >. It can be used in documentation as a prompt indicator without triggering a shelldoc test.

Installation

The usual way to install shelldoc is using go get:

$ go get -u github.com/endocode/shelldoc/cmd/shelldoc
...

Executing documentation may have side effects. For example, running this go get command just installed the latest version of shelldoc in your system. Containers or VMs can be used to isolate such side effects.

Details and syntax

All code blocks in the Markdown input are evaluated and executed as tests. A test succeeds if it returns the expected exit code, and the output of the command matches the response specified in the code block.

shelldoc supports both simple and fenced code blocks. An ellipsis, as used in the description on how to install shelldoc above, indicates that all output is accepted from this point forward as long as the command exits with the expected return code (zero, by default).

The -v (--verbose) flags enables additional diagnostic output.

A shell is launched that will execute all shell commands in a single Markdown file. By default, the user's configured shell is used. A different shell can be specified using the -s (--shell) flag:

% shelldoc --verbose --shell=/bin/sh README.md
Note: Using user-specified shell /bin/sh.
...

The shell's lifetime is that of the test run of a single Markdown file. The environment of the shell is available between test interactions:

$ export GREETING="Hello World"
$ echo $GREETING
Hello World

shelldoc uses the Blackfriday Markdown processor to parse Markdown files, and the pflag package to parse the command line arguments.

Options

Regular code blocks do not have a way to specify options. The only thing that can be specified about them are the commands and the responses. That means the expected return code must always be zero for the test to succeed≥

Sometimes, however, things are more complicated. Some commands are expected to return a different exit code than zero. Some commands return exit codes that are unknown up-front. Both options can be handled by specifying tests in fenced code blocks. Fenced code blocks may have an info string after the opening characters. This info string is usually used to specify the language of the following code. After the language specifier however, other information may follow. shelldoc uses this opportunity to allow the user to specify options about the test. These options are:

```shell {shelldocwhatever}
% echo Hello && false
Hello
```

Try executing this test:

> echo Hello && false
Hello

The shelldocwhatever options tells shelldoc that the exit code of the following command does not matter. If any expected response is specified, it will still be evaluated.

```shell {shelldocexitcode=2}
% (exit 2)
```

This executes the test, for tests:

> (exit 2)

The shelldocexitcode specifies an exact exit code that is expected. The test fails if the exit code of the command does not match the specified one, or if the response does not match the expected response.

Contributing

shelldoc is free and open source software. Everybody is invited to use, study, modify and redistribute it. To contribute to shelldoc, feel free to fork it and submit pull requests, or to submit issues in the shelldoc issue tracker. All contributions are welcome.

To report a bug, the best way is to submit a Markdown file and a description of how the Markdown file should be interpreted, and how shelldoc interprets it.

Authors and license

shelldoc was developed by Mirko Boehm. Commercial support, if necessary, is provided by Endocode.

The command line programs of shelldoc are located in the cmd/ subdirectory and licensed under the terms of the GPL, version 3. The reusable components are located in the pkg/ subdirectory and licensed under the terms of the LGPL version 3. Unit test and example code is licensed under the Apache-2.0 license.