Marked Conductor

A “train conductor” for Marked 2 (Mac only). Conductor can be set up as a Custom Preprocessor or Custom Processor for Marked, and can run different commands and scripts based on conditions in a YAML configuration file, allowing you to have multiple processors that run based on predicates.


$ gem install marked-conductor

If you run into errors, try running with the --user-install flag:

$ gem install --user-install marked-conductor

I’ve noticed lately with asdf that I have to run asdf reshim after installing gems containing binaries.

If you use Homebrew, you can run

$ brew gem install marked-conductor


To use Conductor, you need to set up a configuration file in ~/.config/conductor/tracks.yaml. Run conductor once to create the directory and an empty configuration. See Configuration below for details on setting up your “tracks.”

Once configured, you can set up conductor as a Custom Processor in Marked. Run which conductor | pbcopy to get the full path to the binary and copy it, then open Marked Preferences > Advanced and select either Custom Processor or Custom Preprocessor (or both) and paste into the Path: field. You can select Automatically enable for new windows to have the processor enabled by default when opening documents.

Conductor requires that it be run from Marked 2, and won’t function on the command line. This is because Marked defines special environment variables that can be used in scripts, and these won’t exist when running from your shell. If you want to be able to test Conductor from the command line, see Testing.


Configuration is done in a YAML file located at ~/.config/conductor/tracks.yaml. Run conductor from the command line to generate the necessary directories and sample config file if it doesn’t already exist.

The top level key in the YAML file is tracks:. This is an array of hashes, each hash containing a condition and either a script or command key.

A simple config would look like:

  - condition: yaml includes comments
    script: blog-processor
  - condition: any
    command: echo 'NOCUSTOM'

This would run a script at ~/.config/conductor/scripts/blog-processor if there was YAML present in the document and it included a key called comments. If not, the condition: any would echo NOCUSTOM to Marked, indicating it should skip any Custom Processor. If no condition is met, NOCUSTOM is automatically sent, so this particular example is redundant. In practice you would include a catchall processor to act as the default if no prior conditions were met.

Instead of a script or command, a track can contain another tracks key, in which case the parent condition will branch and it will cycle through the tracks contained in the tracks key for the hash. tracks keys can be repeatedly nested to create AND conditions.

For example, the following functions the same as condition: phase is pre AND tree contains .obsidian AND (extension is md or extension is markdown):

  - condition: phase is pre
    - condition: tree contains .obsidian
      - condition: extension is md
        command: obsidian-md-filter
      - condition: extension is markdown
        command: obsidian-md-filter

Adding a title

Tracks can contain a title key. This is only used in the STDERR output of the track, where ‘Met condition: …’ is shown for debugging. If a title is not present, the condition itself will be shown for debugging. If a title is defined, it replaces the condition in the STDERR output. This is mostly for shortening long condition strings to something more meaningful for debugging.


A track can also contain a sequence of scripts and/or commands. STDIN will be passed into the first script/command, then the STDOUT of that will be piped to the next script/command. To do this, add a key called sequence that contains an array of scripts and commands:

  - condition: phase is pro AND path contains
      - script: strip_emoji
      - command: rdiscount

A sequence can not contain nested tracks.

By default, processing stops when a condition is met. If you want to continue processing after a condition is successful, add the continue: true to the track. This will only apply to tracks containing this key, and processing will stop when it gets to a successful condition that doesn’t contain the continue key (or reaches the end of the tracks without another match).


Available conditions are:

  • extension (or ext): This will test the extension of the file, e.g. ext is md or ext contains task
  • tree contains ...: This will test whether a given file or directory exists in any of the parent folders of the current file, starting with the current directory of the file. Example: tree contains .obsidian would test whether there was an .obsidian directory in any of the directories above the file (indicating it’s within an Obsidian vault)
  • path: This tests just the path to the file itself, allowing conditions like path contains _drafts or path does not contain _posts.
  • filename: Tests only the filename, can be any string comparison (starts with, is, contains, etc.).
  • phase: Tests whether Marked is in Preprocessor or Processor phase, allowing conditions like phase is preprocess or phase is process (which can be shortened to pre and pro).
  • text: This tests for any string match within the text of the document being processed. This can be used with operators starts with, ends with, or contains, e.g. text contains @taskpaper or text does not contain <!--more-->.
    • If the test value is surrounded by forward slashes, it will be treated as a regular expression. Regexes are always flagged as case insensitive. Use it like text contains /@\w+/.
  • yaml, headers, or frontmatter will test for YAML headers. If a yaml:KEY is defined, a specific YAML key will be tested for. If a value is defined with an operator, it will be tested against the value key.
    • yaml tests for the presence of YAML frontmatter.
    • yaml:comments tests for the presence of a comments key.
    • yaml:comments is true tests whether comments: true exists.
    • yaml:tags contains appreview will test whether the tags array contains appreview.
    • If the YAML key is a date, it can be tested against with before, after, and is, and the value can be a natural language date, e.g. yaml:date is after may 3, 2024
    • If both the YAML key value and the test value are numbers, you can use operators greater than (>), less than (<), equal/is (=/==), and is not equal/not equals (!=/!==). Numbers will be interpreted as floats.
    • If the YAML value is a boolean, you can test with is true or is not true (or is false)
  • mmd or meta will test for MultiMarkdown metadata using the same formatting as yaml above.
  • The following keywords act as a catchall and can be used as the last track in the config to act on any documents that aren’t matched by preceding rules:
    • any
    • else
    • all
    • true
    • catchall

Available comparison operators are:

  • is or equals (negate with is not or does not equal) tests for equality on strings, numbers, or dates
  • contains or includes (negate with does not contain) tests on strings or array values
  • begins with (or starts with) or ends with (negate with does not begin with) tests on strings
  • greater than or less than (tests on numbers or dates)

Conditions can be combined with AND or OR (must be uppercase) and simple parenthetical operations will work (parenthesis can not be nested). A boolean condition would look like path contains _posts AND extension is md or (tree includes .obsidian AND extension is todo) OR extension is taskpaper.


The action can be script, command, or filter.


Scripts are located in ~/.config/conductor/scripts/ and should be executable files that take input on STDIN (unless $file is specified in the script definition). If a script is defined starting with ~ or /, that will be interpreted as a full path to an alternate location.


script: github_pre


Commands are interpreted as shell commands. If a command exists in the $PATH, a full path will automatically be determined, so a command can be as simple as just pandoc. Add any arguments needed after the command.


command: multimarkdown

Using $file as an argument to a script or command will bypass processing of STDIN input, and instead use the value of $MARKED_PATH to read the contents of the specified file.


Filters are simple actions that can be run on the content without having to write a separate script for it. Available filters are:

filter description
setMeta(key, value) adds or updates a meta key, aware of YAML and MMD
stripMeta strips all metadata (YAML or MMD) from the content
deleteMeta(key) removes a specific key (YAML or MMD)
setStyle(name) sets the Marked preview style to a preconfigured Style name
replace(search, replace) performs a (single) search and replace on content
replaceAll(search, replace) global version of replaceAll)
insertTitle adds a title to the document, either from metadata or filename
insertScript(path[,path]) injects javascript(s)
insertTOC(max, after) insert TOC (max=max levels, after=start, *h1, or h2)
prepend/appendFile(path) insert a file as Markdown at beginning or end of content
prepend/appendRaw(path) insert a file as raw HTML at beginning or end of content
prepend/appendCode(path) insert a file as a code block at beginning or end of content
insertCSS(path) insert custom CSS into document
autoLink() Turn bare URLs into <self-linked> urls
fixHeaders() Reorganize headline levels to semantic order

For replace and replaceAll: If search is surrounded with forward slashes followed by optional flags (i for case-insensitive, m to make dot match newlines), e.g. /contribut(ing)?/i, it will be interpreted as a regular expression. The replace value can include numeric capture groups, e.g. Follow$2.

For insertScript, if path is just a filename it will look for a match in ~/.config/conductor/javascript or ~/.config/conductor/scripts and turn that into an absolute path if the file is found.

For insertCSS, if path is just a filename (with or without .css extension), the file will be searched for in ~/.config/conductor/css or ~/.config/conductor/files and injected. CSS will be compressed using the YUI algorithm and inserted at the top of the document, but after any existing metadata.

For insertTitle, if an argument of true or a number is given (e.g. insertTitle(true), the headers in the document will be shifted by 1 (or by the number given) so that there’s only one H1 in the document.

If the path for insertScript or insertCSS is a URL instead of a filename, the URL will be properly inserted instead of a file path. Inserted scripts will be surrounded with <div> tags, which fixes a quirk with javascript in Marked.

For all of the prepend/append file filters, you can store files in ~/.config/conductor/files and reference them with just a filename. Otherwise a full path will be assumed.

For autoLink, any URL that’s not contained in parenthesis or following a []: url pattern will be autolinked (surrounded by angle brackets). URLs must contain // to be recognized, but any protocol will work, e.g. x-marked://refresh. Must be run on Markdown (prior to any postprocessor HTML conversion).

For fixHeaders, it will be ensured that the document has an h1, and all header levels will be adapted to never jump more than one header level when increasing. If no H1 exists in the document, the first header of the lowest existing level will be turned into an H1 and all other headers will be decremented to fit the hierarchy. It’s not perfect, but it does a pretty good job. When saving the document as Markdown from Marked, the new headers will be applied. Must be run on Markdown (prior to any postprocessor HTML conversion).

Note: successive filters in a sequence that insert or prepend will always insert content before/above the result of the previous insert filter. So if you have an insertTitle filter followed by an insertCSS filter, the CSS will appear above the inserted title. If you want elements inserted in reverse order, reverse the order of the inserts in the sequence.


filter: setStyle(github)

Filters can be camel case (replaceAll) or snake case (replace_all), either will work, case insensitive.

Custom Processors

All of the capabilities and requirements of a Custom Processor script or command still apply, and all of the environment variables that Marked sets are still available. You just no longer have to have one huge script that forks on the various environment variables and you don’t have to write your own tests for handling different scenarios.

A script run by Conductor already knows it has the right type of file with the expected data and path, so your script can focus on just processing one file type. It’s recommended to separate all of that logic you may already have written out into separate scripts and let Conductor handle the forking based on various criteria.

Custom processors must wait for input on STDIN. Most markdown CLIs will do this automatically, but scripts should include a call to read STDIN. This will pause the script and wait for the data to be sent. Without this, Marked will launch the script, and if it closes the pipe, it will try to write data to a closed pipe and crash immediately. This is a very difficult error to trap in Marked, so it’s crucial that all scripts keep the STDIN pipe open.


  • Config file must be valid YAML. Any value containing colons, brackets, or other special characters should be quoted, e.g. (condition: "text contains my:text")
  • You can see what condition matched in Marked by opening Help->Show Custom Processor Log and checking the STDERR output.
  • To run a custom processor for Bear, use the condition "text contains <!-- source: -->". You might consider running a commonmark CLI with Bear to support more of its syntax.
  • To run a custom processor for Obsidian, use the condition tree contains .obsidian


You can test conductor setups using Marked’s Help->Show Custom Processor Log, or by running from the command line. The easiest way to test conditions is to set the track’s command to echo "meaningful definition" and see what conditions are met when conductor is run.

In Marked’s Custom Processor Log, you can see both the STDOUT output and the STDERR messages. When running Conductor, the STDERR output will show what conditions were met (as well as any errors reported).

From the command line

There’s a script included in the repo called that will take a file path as an argument and set all of the environment variables for testing. Run -h for usage instructions.

In order to test from the command line, you’ll need certain environment variables set. This can be done by exporting the following variables with your own definitions, or by running conductor with all of the variables preceding the command, e.g. $ MARKED_ORIGIN=/path/to/ [...] conductor.

The following need to be defined. Some can be left as empty or to defaults, such as MARKED_INCLUDES and MARKED_OUTLINE, but all need to be set to something.

MARKED_CSS_PATH="" # The path to CSS, can be empty
MARKED_EXT="md" # The extension of the current file in Marked, set as needed for testing
MARKED_INCLUDES="" # Files included in the document, can be empty
MARKED_ORIGIN="/Users/ttscoff/notes/" # Base directory for the file being tested
MARKED_PATH="/Users/ttscoff/notes/" # Full path to Markdown file
OUTLINE="none" # Outline mode, can be "none"
PATH=$PATH # The system $PATH variable

Further, input on STDIN is required, unless the script/command being matched contains $file, in which case $MARKED_PATH will be read and operated on. For the purpose of testing, you can use echo or cat FILE and pipe to conductor, e.g. echo "TESTING" | conductor.

To test which conditions are being met, you can just set the command: for a track to echo "meaningful message", where the message is something that indicates which condition(s) have passed.


Click to expand


2024-07-10 12:18


  • New filter fixHeaders will adapt all headlines in the document to be in semantic order


2024-07-04 12:18


  • The insertTitle filter can now take an argument of true or a number and will shift the remaining headlines in the document by 1 (or the number given in the argument), allowing for title insertion while only having 1 H1 in the document.


  • Ignore self-linking urls in single quotes, just in case they’re used in a script line


2024-07-02 11:25


  • Bug in creating default config


2024-07-02 11:08


  • InsertScript or insertCSS arguments that are URLs will be inserted properly


  • When prepending styles/files/titles, always inject AFTER existing metadata (YAML or MMD)


2024-07-02 10:27


  • AutoLink() filter will self-link bare URLs


2024-06-28 12:40


  • New insertCSS filter to inject a stylesheet
  • YUI compression for injected CSS


2024-05-25 11:14


  • New filter insertTOC(max, after) to insert a table of contents, optionally with max levels and after (start, *h1, or h2)
  • New filter prepend/appendFile(path) to include a file (also pre/appendRaw and pre/appendCode)


2024-05-25 06:41


  • InsertTitle filter will extract title from metadata or filename and insert an H1 title into the content
  • InsertScript will inject a javascript at the end of the content, allows passing multiple scripts separated by comma, and if the path is just a filename, it will look for it in ~/.config/conductor/javascript and insert an absolute path


2024-05-24 13:12


  • New type of command – filter: filterName(parameters), allows things like setStyle(github) or replace_all(regex, pattern) instead of having to write scripts for simple things like this. Can be run in sequences.


2024-05-01 13:06


  • Attempt to fix encoding error


2024-04-29 09:46


  • Reversed symbols when outputting condition matches to STDERR
  • Only assume date if it’s not part of a filename


2024-04-28 14:05


  • Return NOCUSTOM if changes are not made by scripts/commands, even though condition was matched
  • Use YAML.load instead of .safe_load to allow more flexibility
  • Trap errors reading YAML and fail gracefully


  • Encoding errors on string methods


2024-04-27 16:00


  • Test for pandoc metadata (%%) with is pandoc or is not pandoc


  • Filename comparison not working


2024-04-27 14:01


  • Add sequence: key to allow running a series of scripts/commands, each piping to the next
  • Add continue: true for tracks to allow processing to continue after a script/command is successful
  • filename key for comparing to just filename (instead of full
  • Add is a tests for number, integer, and float
  • Tracks in YAML config can have a title key that will be shown in STDERR ‘Conditions met:’ output
  • Add does not contain handling for string and metadata comparisons


  • Allow has yaml or has meta (MultiMarkdown) as conditions


  • Use STDIN instead of reading file for conditionals
  • String tests read STDIN input, not reading the file itself, allowing for piping between multiple scripts


2024-04-26 11:53


  • Added test for MMD metadata, either for presence of meta or for specific keys or key values


  • Remove some debugging garbage


2024-04-26 11:17


  • Always wait for STDIN or Marked will crash. Still possible to use $file in script/command values
  • More string encoding fixes
  • “path contains” was returning $PATH instead of the filepath


2024-04-25 17:00


  • First-run config creating directory instead of file
  • Frozen string/encoding issue on string comparisons


2024-04-25 14:32


  • YAML true/false testing


2024-04-25 14:15


  • Prepped for gem release


  • Encoding issue affecting Shellwords.escape


2024-04-25 10:51


  • 1.0 release


  • Initial release

Speaking of Conductor…

Related Projects