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+## Shell Script
+
+- Run the [ShellCheck](https://github.com/koalaman/shellcheck) linter
+  on all scripts.
+
+- Follow Google's [Shell Style
+  Guide](https://google.github.io/styleguide/shell.xml); most notably,
+  the below points.
+
+- Use only Bourne Again SHell (Bash).
+
+  It's acceptable to use features available only in Bash 4 and
+  later. As of this writing, that version was released almost 10 years
+  ago, and developers on any platforms which do not ship the latest
+  version out-of-the box are expected to upgrade.
+
+- Prefer no file name extension for executables, and ".sh" extensions
+  for libraries (scripts that are meant to be "sourced" in other
+  scripts).
+
+  Rationale: an OS can run any executable file, regardless of its
+  content, and as such, it isn't helpful to know that an executable is
+  in fact a shell script. However, it is essential to know that an
+  included library is indeed a shell script.
+
+- Use long names for command-line options rather than short
+  ones. E.g. use `ls --all` instead of `ls -a`.
+
+  Rationale: long names trade off clarity at the expense of
+  brevity. They make it easier for an unfamiliar reader to grasp the
+  meaning of an argument, but require the author to write more
+  characters. Hence they are recommended in all places that are read
+  more often than written.
+
+- Use lower_snake_case for all local environment variables, and
+  UPPER_SNAKE_CASE for exported variables.
+  
+- Prefer parsing command line options rather than relying on
+  environment variables for configuration.
+
+- Print status messages to stderr, not stdout.
+
+  Rationale: stdout is often parsed by other utilities (for example in
+  a pipeline) and should hence only contain a program's output, if
+  any.
+
+- Don't make any assumptions about the working directory from which a
+  script is invoked. Specifically, don't require that the script be
+  invoked within the same directory it is located.
+    
+  Rationale: scripts should be treated like any other executable and
+  should support indirection via symlinks. Requiring a specific
+  working directory for a program to function is a needless
+  restriction.
+  
+  Note that this guide specifically applies to the *working directory*
+  of the caller. The script itself may make assumptions about *its
+  location* and the location of resources. The following snippet is an
+  example mechanism to determine the directory of a script.
+  ```bash
+  # Base directory that this script is located at.
+  dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )"
+  ```