A command line interface for generating table of contents for Markdown files.
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Tocer (a.k.a. Table of Contenter) is a command line interface for generating table of contents for Markdown files.

Table of Contents


  • Supports Markdown ATX-style headers. Example: # Header.
    • Does not support header suffixes. Example: # Header #.
    • Does not support header prefixes without spaces. Example: #Header.
  • Supports table of contents generation for single or multiple files.
  • Supports custom label. Default: "## Table of Contents".
  • Supports file list filtering. Default: "README.md".
  • Prepends table of contents to Markdown documents that don't have table of contents.
  • Rebuilds Markdown documents that have existing table of contents.


  1. A UNIX-based system.
  2. Ruby 2.6.x.


Type the following to install:

gem install tocer


Command Line Interface (CLI)

From the command line, type: tocer --help

tocer -c, [--config]         # Manage gem configuration.
tocer -g, [--generate=PATH]  # Generate table of contents.
tocer -h, [--help=COMMAND]   # Show this message or get help for a command.
tocer -v, [--version]        # Show gem version.

For specific --generate options, run tocer --help --generate to see the following:

-l, [--label=LABEL]             # Label
                                # Default: ## Table of Contents
-i, [--includes=one two three]  # File include list
                                # Default: ["README.md"]

To generate the table of contents at a specific position within your Markdown files, add the following lines to your file(s) prior to generation:

<!-- Tocer[start] -->
<!-- Tocer[finish] -->

Alternatively, you can run tocer -g <directory> on files that do not have Tocer support and it will prepend the table of contents to your file(s), complete with an auto-generated table of contents.

In the case that Tocer has already auto-generated a table of contents for a Markdown file, the existing table of contents has become stale, or placement of the table of contents has changed you can re-run Tocer on that file to auto-update it with new table of contents.


This gem can be configured via a global configuration:


It can also be configured via XDG environment variables as provided by the Runcom gem.

The default configuration is as follows:

:label: "## Table of Contents"
  - "README.md"

Feel free to take this default configuration, modify, and save as your own custom configuration.yml.

The configuration.yml file can be configured as follows:

  • label: The header label for the table of contents. Default: "# Table of Contents".
  • includes: The list of included files. Default: "*.md".

There are multiple ways the include list can be defined. Here are some examples:

# Use an empty array to ignore all files (a key with no value would work too).
:includes: []

# Use an array of wildcards for groups of files with similar extensions:
  - "*.md"
  - "*.mkd"
  - "*.markdown"

# Use a mix of wild cards and relative names/paths to customized as necessary:
  - "README.md"
  - "docs/*.md"
  - "*.markdown"

# Use a recursive glob to traverse and update all sub-directories:
  - "**/*.md"


To test, run:

bundle exec rake


Read Semantic Versioning for details. Briefly, it means:

  • Major (X.y.z) - Incremented for any backwards incompatible public API changes.
  • Minor (x.Y.z) - Incremented for new, backwards compatible, public API enhancements/fixes.
  • Patch (x.y.Z) - Incremented for small, backwards compatible, bug fixes.

Code of Conduct

Please note that this project is released with a CODE OF CONDUCT. By participating in this project you agree to abide by its terms.


Read CONTRIBUTING for details.


Copyright 2015 Alchemists. Read LICENSE for details.


Read CHANGES for details. Built with Gemsmith.


Developed by Brooke Kuhlmann at Alchemists.