bash_docstring

Docstrings for Shell/Bash

Docstrings are extremely useful for centralising documentation in one place, helping to standarise the content that appears in READMEs, manpages and command-line help.

Bash docstrings are a semantic near-equivalent of Python docstrings. The bash_docstring script/function thus emulates Python's __doc__.

Bash Docstring Structure

[[function ]funcname[ ]()]
[#!hashbangs]
[#shellchecks]
[]
[#non-docstring comment]
# docstring comment '# '
# docstring comment
# docstring comment
# ...
# ...
commands #docstrings stop when commands start.
...

All hashbangs, shellchecks, blank lines and non-docstring comments are ignored while processing the docstring. Docstring processing stops with the first command.

To test bash_docstring's functionality, use bash_docstring itself:

# Display the bash_docstring's script docstring
bash_docstring

# Display a script's docstring specifying a source file,
# and with parameter expansion (-e).
bash_docstring -e bash_docstring.bash

# Display the docstring for the bash_docstring function
# in script file bash_docstring.bash,
# with parameter expansion (-e).
bash_docstring -e bash_docstring.bash bash_docstring

bash_docstring is designed to extract and display docstrings from a Bash script or function. The concept of docstrings here is similar to Python, where documentation is embedded within the code.

The -e switch determines whether to eval docstring lines, useful if you wish to include display of current variables within the docstring. This can be very useful for dynamic help text. Note: '``' and '$ (' are disabled. See warnings below.

If no function name specified, then bash_docstring looks for the docstring at the start of the script file. If a function name is provided, it searches for the docstring associated with that function within the source file.

Error Handling and Output

If the script fails to find a docstring, it outputs a message and returns an error.

Security Considerations

The use of -e|--eval can be risky if not handled carefully. docstring attempts to mitigate this risk by escaping '``' and '$ (' characters, but users should still be cautious, especially when dealing with untrusted input.

Version: 0.4.20(25)-beta

Updated: 2023-11-30

Author: Gary Dean

Organisation: Open Technology Foundation

Licence: GPL3

Repository: https://github.com/Open-Technology-Foundation/bash_docstring

bash_docstring Script/Function

Displays docstring from a Bash script, or function within a Bash script docstring, directly from script source file.

bash_docstring is a robust way to organise script and function documentation in a more standardized and consistent manner, using the well-known conventions and protocols of contemporary computer programming.

bash_docstring is written using 100% core Bash. The in-memory size of the function is less than 2.5K.

In typical usage, the bash_docstring function is simply sourced or copied into your application script as a replacement for usage() or help().

Usage

bash_docstring [-e] [source_file [function_name]]

-e, --eval
    Execute `eval` for each docstring line. (Default is no
    `eval`.) Escape '$' chars as required, otherwise Bash
    parameter expansion will take place. Note: All '``'
    and '""' chars in the docstring are escaped when `-e` is
    used.

source_file
    Name of script file in which to search for a docstring. If
    not specified, `source_file` defaults to $PRG0
    (if present), which otherwise falls back to $0.

function_name
    Name of a function within `source_file`. If
    `function_name` is not defined or empty, then the
    docstring for the script `source_file` is displayed. If
    defined, then the docstring for the `function_name`
    function is displayed, and 0 returned. If a docstring is
    not found, an error message is displayed and 1 is
    returned.

bash_docstring reads source_file for all contiguous comments at the top of the script or (optionally) immediately after a function definition.

Docstring comments are indicated with '# ' (hash-space). Leading white-space is ignored.

Hashbangs, shellchecks and 'empty' comment lines are all ignored. Docstring processing stops at the first command in the script or function.

Docstrings are output to stdout minus leading hash-space '# '.

Examples:

./bash_docstring

./bash_docstring -e

./bash_docstring -h

./bash_docstring bash_docstring

./bash_docstring -e bash_docstring.bash bash_docstring

./bash_docstring -e "" bash_docstring

./bash_docstring /my/dir/myscript