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# Introduction

`make4ht` is a simple build system for `tex4ht`, \TeX\ to XML converter. It provides a command line tool
that drive the conversion process. It also provides a library which can be used to create
customized conversion tools. An example of such conversion tool is
[tex4ebook](https://github.com/michal-h21/tex4ebook) for conversion of \TeX\ to
ePub and other e-book formats.


## How it works

### The issues with default `tex4ht` conversion commands


`tex4ht` system supports several output formats, most notably `XHTML`, `HTML 5` and `ODT`. 
The conversion can be invoked using several commands. These commands invoke LaTeX\ or Plain TeX 
with special instructions to load `tex4ht.sty` package. The \TeX\ run produces special `DVI` file 
which contains the code for desired output format. Produced `DVI` file is then processed and 
desired output files are created.

The basic command provided by `tex4ht` is named `htlatex`. It  compiles \LaTeX\  
files to `HTML` with this command sequence:

    latex $latex_options 'code for loading tex4ht.sty \input{filename}'
    latex $latex_options 'code for loading tex4ht.sty \input{filename}'
    latex $latex_options 'code for loading tex4ht.sty \input{filename}'
    tex4ht $tex4ht_options filename
    t4ht $t4ht_options filename

The options for various parts of the system can be passed on the command line:

    htlatex filename "tex4ht.sty options" "tex4ht_options" "t4ht_options" "latex_options"

For basic `HTML` conversion it is possible to use the most basic invocation:

    htlatex filename.tex

It can be much more involved for `HTML 5` output in `UTF-8` encoding:

    htlatex filename.tex "xhtml,html5,charset=utf-8" "-cmozhtf -utf8"

`make4ht` can simplify it:

    make4ht -uf html5 filename.tex

Another issue is the fixed compilation order and hard-coded number of LaTeX invocations.

When you need to run a program which interact with LaTeX, such as `Makeindex`
or `Bibtex`, you need to create a new script based on `htlatex`, or run
`htlatex` twice, which means that LaTeX will be invoked six times. 
This can lead to significantly long compilation times. `make4ht` provides build files and
extensions, which can be used for interaction with external tools.

It is also possible to have several compilation modes. When you just add new text to a document, 
which doesn't contain cross-references, don't add new stuff to the table of contents, etc., 
it is possible to use the `draft` mode which will invoke LaTeX only once. It
can save quite a lot of the compilation time:

    make4ht -um draft -f html5 filename.tex

There are also issues with a behaviour of the `t4ht` application. It reads file
`filename.lg`, generated by `tex4ht`, where are instructions about generated
files, `CSS` instructions, calls to external applications, instructions for
image conversions etc. It can be instructed to copy generated files to some
output directory, but it doesn't preserve directory structure, so when you
have images in a subdirectory, they will be copied to the output directory.
Links will be pointing to a non-existing subdirectory. The following command
should copy all output files to the correct destinations.

    make4ht -d outputdir filename.tex

The image conversion is configured in the
[env file](http://www.tug.org/applications/tex4ht/mn35.html#index35-73001),
which has really strange syntax based and the rules are 
[os dependent](http://www.tug.org/applications/tex4ht/mn-unix.html#index27-69005).
`make4ht` provides simpler means for the image conversion in the build files.

With `make4ht` build files, we have simple mean to fix these issues. We can
change image conversion parameters without the need to modify the `env file`,
or execute actions on the output files. These actions can be either external
programs such as `xslt` processors or `HTML tidy` or `Lua` functions.

The idea is to make system controlled by a build file. Because `Lua`
interpreter is included in modern TeX distributions and `Lua` is ideal language
for such task, it was chosen as language in which the build scripts are written.

# Output file formats and extensions

The default output format used by `make4ht` is `html5`. Different
format can be requested using the `--format` option. Supported formats are:

 - `xhtml`
 - `html5`
 - `odt`
 - `tei`
 - `docbook`

The `--format` option can be also used for extension loading.

## Extensions

Extensions can be used to modify the build process without the need to use a build file. They
may post-process the output files or request additional commands for the compilation.

The extensions can be enabled or disabled by appending `+EXTENSION` or `-EXTENSION` after
the output format name:

     make4ht -uf html5+tidy filename.tex

Available extensions:

latexmk_build

:    use `Latexmk` for \LaTeX\ compilation.

tidy

:    clean the `HTML` files using the `tidy` command.

dvisvgm_hashes

:    efficient generation of SVG pictures using Dvisvgm. It can utilize
multiple processor cores and generates only changed images.

common\_filters

:    clean the output HTML files using filters.

common\_domfilters

:    clean the HTML file using DOM filters. It is more powerful than
`common_filters`. Used DOM filters are `fixinlines`, `idcolons` and
`joincharacters`.

join\_colors

:    load the `joincolors` domfilter for all HTML files.

mathjaxnode

:    use [mathjax-node-page](https://github.com/pkra/mathjax-node-page/) to
     convert from MathML code to HTML + CSS or SVG. See [the available
     settings](#mathjaxsettings).

odttemplate

:    automatically load the `odttemplate` filter.

staticsite

:    build the document in form suitable for static site generators like [Jekyll](https://jekyllrb.com/).

# Build files

`make4ht` supports build files. These are `Lua` scripts which can adjust
the build process. You can request external applications like `bibtex` or `makeindex`,
pass options to the commands, modify the image conversion process, or post-process the
generated files.

`make4ht` tries to load default build file named as `filename + .mk4 extension`.
You can choose different build file with `-e` or `--build-file` command line
option.

Sample build file:

    Make:htlatex()
    Make:match("html$", "tidy -m -xml -utf8 -q -i ${filename}")

`Make:htlatex()` is preconfigured command for calling LaTeX with `tex4ht`
loaded on the input file. In this case, it will be called  one time. After
compilation, the `tidy` command is executed on the output `HTML` file.

Note that you don't have to call `tex4ht` and `t4ht` commands explicitly in the
build file, they are called automatically. 

## User commands

You can add more commands like `Make:htlatex` using `Make:add` command:

    Make:add("name", "command", {parameters}, repetition)

The `name` and `command` parameters are required, rest of the parameters are optional.

This defines `name` command, which can be then executed as `Make:name()` command.

### Provided commands

`Make:htlatex`

:    One call to TeX engine with special configuration for `tex4ht` loading.

`Make:latexmk`

:    Use `Latexmk` for the document compilation. `tex4ht` will be loaded automatically.

`Make:tex4ht`

:    Process the `DVI` file and creates the output files.

`Make:t4ht`

:    Creates the CSS file.


### Command function

The `command` parameter can be either string template or function:

    Make:add("text", "echo hello, input file: ${input}")
    Make:add("function", function(params) 
      for k, v in pairs(params) do 
        print(k..": "..v) 
      end, {custom="Hello world"}
    )

The template can get variable value from the parameters table using a
`${var_name}` placeholder. Templates are executed using operating system, so
they should invoke existing OS commands. Function commands may execute system
commands using `os.execute` function.


### Parameters table

`parameters` parameter is optional, it can be table or `nil` value, which
should be used if you want to use the `repetition` parameter, but don't want to
modify the parameters table. 

The table with default parameters is passed to all commands, they can be accessed from command functions
or templates. When you specify your own parameters in the command definition, these additional
parameters are added to the default parameters table for this particular
command. You can override the default parameters in the parameters table.



The default parameters are following:

`htlatex`

:     used compiler

`input`

:    it is output file name in fact

`tex_file`

:    input TeX file

`latex_par`

:    parameters to `latex`

`packages`

:    insert additional LaTeX code which is inserted before `\documentclass`.
     Useful for passing options to packages or additional packages loading

`tex4ht_sty_par`

:    parameters to `tex4ht.sty`

`tex4ht_par`

:     parameters to the `tex4ht` application

`t4ht_par`

:    parameters to the `t4ht` application

`outdir`

:    the output directory

`repetition`

:    limit number of command execution.

`correct_exit`

:    expected `exit code` from the command. The compilation will be terminated
     if the command `exit code` is different.


### Repetition

Repetition is number which specifies a maximal number of executions of the
particular command.  This is used for instance for `tex4ht` and `t4ht`
commands, as they should be executed only once in the compilation. They would
be executed multiple times if you include them in the build file because they
are called by `make4ht` by default. Because these commands allow only one
`repetition`, the second execution will be blocked.

### Expected exit code

You can set the expected exit code from a command with a `correct_exit` key in the
parameters table. The compilation will be stopped when the command returns a
different exit code. 

This mechanism isn't used for LaTeX (for all TeX engines and formats, in
fact), because it doesn't differentiate between fatal and non-fatal errors, and
it returns the same exit code in all cases. Log parsing is used because of
that, error code `1` is returned in the case of fatal error, `0` is used
otherwise. The `Make.testlogfile` function can be used in the build file to
detect compilation errors in the TeX log file.

## File matches

Another type of action which can be specified in the build file is
`match`.  It can be called on the generated files:

    Make:match("html$", "tidy -m -xml -utf8 -q -i ${filename}")

It tests output file names with `Lua` pattern matching and on matched items will
execute a command or a function, specified in the second argument. Commands may be
specified as strings, the templates will be expanded, `${var_name}` placeholders
will be replaced with corresponding variables from the `parameters` table,
described in the previous subsection. One additional variable is available:
`filename`. It contains the name of the current output file.

The above example will clean all output `HTML` files using the `tidy` command.

If function is used instead, it will get two parameters.
The first one is a current filename, the second one
table with parameters. 



### Filters

Some default `match` actions which can be used are available from  the
`make4ht-filter` module.  It contains some functions which are useful for
fixing some `tex4ht` bugs or shortcomings.

Example:

    local filter = require "make4ht-filter"
    local process = filter{"cleanspan", "fixligatures", "hruletohr"}
    Make:htlatex()
    Make:htlatex()
    Make:match("html$",process)

The `make4ht-filter` module return a function which can be used for the filter
chain building. Multiple filters can be chained, each of them can modify the string
which was modified by the previous filters. The changes are then saved to the
processed file.

Built-in filters are:

cleanspan

:    clean spurious span elements when accented characters are used

cleanspan-nat

:    alternative clean span filter, provided by Nat Kuhn

fixligatures

:    decompose ligatures to base characters

hruletohr

:   `\hrule` commands are translated to series of underscore characters
    by `tex4ht`, this filter translate these underscores to `<hr>` elements

entites

:    convert prohibited named entities to numeric entities (currently, only
     `&nbsp;`, as it causes validation errors, and `tex4ht` is producing it
     sometimes)

fix-links

:    replace colons in local links and `id` attributes with underscores. Some
     cross-reference commands may produce colons in internal links, which results in
     validation error.

mathjaxnode

:    use [mathjax-node-page](https://github.com/pkra/mathjax-node-page/) to
     convert from MathML code to HTML + CSS or SVG. See [the available
     settings](#mathjaxsettings).

odttemplate

:    use styles from another `ODT` file serving as a template in the current
     document. It works for the `styles.xml` file in the `ODT` file. During
     the compilation, this file is named as `\jobname.4oy`.

staticsite

:    create HTML files in format suitable for static site generators such as [Jekyll](https://jekyllrb.com/)

svg-height

:    some  SVG images produced by `dvisvgm` seem to have wrong dimensions. This filter
     tries to set the correct image size.

Function `filter` accepts also function arguments, in this case this function
takes file contents as a parameter and modified contents are returned.

Example:

    local filter  = require "make4ht-filter"
    local changea = function(s) return s:gsub("a","z") end
    local process = filter{"cleanspan", "fixligatures", changea}
    Make:htlatex()
    Make:htlatex()
    Make:match("html$",process)

In this example, spurious span elements are joined, ligatures are decomposed,
and then all letters 'a' are replaced with 'z' letters.

### DOM filters

DOM filters use the [`LuaXML`](https://ctan.org/pkg/luaxml) library to modify
directly the XML object. This enables more powerful
operations than the regex based filters from the previous section. 

Example:

    local domfilter = require "make4ht-domfilter"
    local process = domfilter {"joincharacters"}
    Make:match("html$", process)


Available DOM filters:

aeneas

:  [Aeneas](https://www.readbeyond.it/aeneas/) is a tool for automagical synchronization of text and audio.
   This filter modifies the HTML code to support the synchronization.

fixinlines

:  put all inline elements which are direct children of the `<body>` elements to a paragraph.

idcolons

:  replace the colon (`:`) character in internal links and `id` attributes. They cause validation issues.

joincharacters

:  join consecutive `<span>` or `<mn>` elements.

joincolors

:  many `<span>` elements with unique `id` attribute are created when \LaTeX\ colors are being used in the document.
   CSS rule is added for each of these elements, which may result in
   substantial grow of the CSS file. This filter replace these rules with a
   common one for elements with the same color value.

odtimagesize

:  set correct dimensions for images in the ODT format. It is loaded by default for the ODT output.

t4htlinks

:  fix hyperlinks in the ODT format.

### make4ht-aeneas-config package

Companion for the `aeneas` DOM filter is the `make4ht-aeneas-config` plugin. It
can be used to write Aeneas configuration file or execute Aeneas on the
generated HTML files.

Available functions:

write\_job(parameters)

:  write Aenas job configuration to `config.xml` file. See the [Aeneas
   documentation](https://www.readbeyond.it/aeneas/docs/clitutorial.html#processing-jobs)
   for more information about jobs.

execute(parameters)

:  execute Aeneas.

process\_files(parameters)

:  process the audio and generated subtitle files.


By default, the `smil` file is created. It is assumed that there is audio file
in `mp3` format named as the TeX file. It is possible to use different formats
and file names using mapping.

The configuration options can be passed directly to the functions or set using
`filter_settings "aeneas-config" {parameters}` function.


Available parameters:


lang 

:  document language. It is interfered from the HTML file, so it is not necessary to set it. 

map 

:  mapping between HTML, audio and subtitle files. More info bellow. 

text\_type 

:  type of the input. The `aeneas` DOM filter produces `unparsed` text type.

id\_sort 

:  sorting of id attributes. Default value is `numeric`.

id\_regex 

:  regular expression to parse the id attributes.

sub\_format 

:  generated subtitle format. Default `smil`.


Additional parameters for the job configuration file:

- description 
- prefix 
- config\_name 
- keep\_config 



It is possible to generate multiple HTML files from the LaTeX source. For
example, `tex4ebook` generates separate file for each chapter or section. It is
possible to set options for each HTML file, in particular names of the
corresponding audio files. This mapping is done using `map` parameter. 

Example:

    filter_settings "aeneas-config" {
      map = {
        ["sampleli1.html"] = {audio_file="sample.mp3"}, 
        ["sample.html"] = false
      }
    }

Table keys are the configured file names. It is necessary to insert them as
`["filename.html"]`, because of Lua syntax rules.

This example maps audio file `sample.mp3` to a section subpage. The main HTML
file, which may contain title and table of contents doesn't have a
corresponding audio file.

Filenames of the sub files corresponds to the chapter numbers, so they are not
stable when a new chapter is added. It is possible to request file names
interfered from the chapter titles using the `sec-filename` option or `tex4ht`.

Available `map` options:


audio\_file 

:  the corresponding audio file 

sub\_file 

:  name of the generated subtitle file

The following options are same as their counter-parts from the main parameters table and generally don't need to be set:

- prefix 
- file\_desc 
- file\_id 
- text\_type 
- id\_sort
- id\_prefix 
- sub\_format 


Full example:


    local domfilter = require "make4ht-domfilter"
    local aeneas_config = require "make4ht-aeneas-config"
    
    filter_settings "aeneas-config" {
      map = {
        ["krecekli1.xhtml"] = {audio_file="krecek.mp3"}, 
        ["krecek.xhtml"] = false
      }
    }
    
    local process = domfilter {"aeneas"}
    Make:match("html$", process)

    if mode == "draft" then
      aeneas_config.process_files {}
    else
      aeneas_config.execute {}
    end




## Image conversion

It is possible to convert parts of LaTeX input to pictures, it is used
for example for math or diagrams in `tex4ht`. 

These pictures are stored in a special `dvi` file, which can be processed by
the `dvi to image` commands. 

This conversion is normally configured in the `env file`,
which is system dependent and which has a bit unintuitive syntax.
This configuration is processed by the `t4ht` application and conversion
commands are called for all pictures.

It is possible to disable `t4ht` image processing and configure image
conversion in the build file:

    Make:image("png$",
    "dvipng -bg Transparent -T tight -o ${output}  -pp ${page} ${source}")


`Make:image` takes two parameters, pattern to match image name and action.
Action can be either string template with conversion command,
or function which takes a table with parameters as an argument.

There are three parameters:

  - `output` - output image file name
  - `source` - `dvi` file with the pictures
  - `page`   - page number of the converted image

## The `mode` variable

There is global `mode` variable available in the build file. It contains
contents of the `--mode` command line option.  It can be used to run some commands
conditionally. For example:

     if mode == "draft" then
       Make:htlatex{} 
     else
       Make:htlatex{}
       Make:htlatex{}
       Make:htlatex{}
     end

In this example (which is the default configuration used by `make4ht`),
LaTeX is called only once when `make4ht` is called with `draft` mode:
    
    make4ht -m draft filename

## The `settings` table

You may want to access to the parameters also outside commands, file matches
and image conversion functions. For example, if you want to convert your file to
the `OpenDocument Format (ODT)`, you can use the following settings, based on the `oolatex`
command:

    settings.tex4ht_sty_par = settings.tex4ht_sty_par ..",ooffice"
    settings.tex4ht_par = settings.tex4ht_par .. " ooffice/! -cmozhtf"
    settings.t4ht_par = settings.t4ht_par .. " -cooxtpipes -coo "

There are some functions to ease access to the settings:

`set_settings{parameters}`

:   overwrite settings with values from a passed table

`settings_add{parameters}`

:   add values to the current settings 

`filter_settings "filter name" {parameters}`

:   set settings for a filter

`get_filter_settings(name)`

:   get settings for a filter


Using these functions, it is possible to simplify the settings for the `ODT` format:

    settings_add {
      tex4ht_sty_par =",ooffice",
      tex4ht_par = " ooffice/! -cmozhtf",
      t4ht_par = " -cooxtpipes -coo "
    }

Settings for filters and extensions can be set using `filter_settings`:

    
    filter_settings "test" {
      hello = "world"
    }

These settings can be read in the extensions and filters using `get_filter_settings`:

    function test(input)
       local options = get_filter_settings("test")
       print(options.hello)
       return input
    end
       
## List of available settings for filters and extensions.

These settings may be set using `filter_settings` function.

### The `tidy` extension

options

:  command line options for the `tidy` command. Default value is `-m -utf8 -w 512 -q`.

### The `fixinlines` dom filter 

inline\_elements

:  table of inline elements which shouldn't be direct descendants of the `body` element. The element names should be table keys, the values should be true.

Example

    filter_settings "fixinlines" {inline_elements = {a = true, b = true}}

### The `joincharacters` dom filter

charelements 

:  table of elements which should be joined if several instances with the same value of `class` attribute are side by side.

Example

    filter_settings "joincharacters" { charclases = { span=true, mn = true}}

### The `mathjaxnode` filter {#mathjaxsettings}

options

:  command line options for the `mjpage` command. Default value is `--output CommonHTML`

Example

    filter_settings "mathjaxnode" {
      options="--output SVG --font Neo-Euler"
    }

cssfilename  

:  `mjpage` puts some CSS code into the HTML pages. `mathjaxnode` extracts this information and saves it to a standalone CSS file. Default CSS filename is `mathjax-chtml.css`

fontdir

:  directory with MathJax font files. This option enables use of local fonts, which
   is usefull in Epub conversion, for example. The font directory should be
   sub-directory of the current directory. Only TeX font is supported at the moment.

Example


    filter_settings "mathjaxnode" {
      fontdir="fonts/TeX/woff/" 
    }

### The `aeneas` filter

skip\_elements

:  List of CSS selectors that match elements which shouldn't be processed. Default value: `{ "math", "svg"}`.

id\_prefix 

:  prefix used in the ID attribute forming.

sentence\_match 

:  Lua pattern used to match a sentence. Default value: `"([^%.^%?^!]*)([%.%?!]?)"`.

### The `staticsite` filter and extension

site\_root 

:  directory where generated files should be copied.

map

:  table where keys are patterns that match filenames, value contains destination directoryfor matched files, relative to the `site_root` (it is possible to use `..` to swich to parent directory).

file\_pattern 

:  pattern used for filename generation. It is possible to use string templates and format strings for `os.date` function. Default value of `%Y-%m-%d-${input}` creates names in the form of `YYYY-MM-DD-file_name`.

header

:  table with variables to be set in the YAML header in HTML files. If the table value is a function, it is executed with current parameters and HTML page DOM object as arguments.

Example:


    local outdir = os.getenv "blog_root" 
    
    filter_settings "staticsite" {
      site_root = outdir, 
      map = {
        [".css$"] = "../css/"
      },
      header = {
         layout="post",
         date = function(parameters, dom)
           return os.date("!%Y-%m-%d %T", parameters.time)
         end
      }
    }

### The `dvisvgm_hashes` extension

options

:  command line options for Dvisvgm. The default value is `-n --exact -c 1.15,1.15`.

cpu_cnt

:  number of processor cores used for conversion. The extension tries to detect the available cores automatically by default.

parallel_size

:  number of pages used in each Dvisvgm call. The extension detects changed pages in the DVI file and construct multiple calls to Dvisvgm with only changed pages.

scale

:  SVG scaling.

### The `odttemplate` filter and extension

template

:  filename of the template `ODT` file 


`odttemplate` can also get the template filename from the `odttemplate` option from `tex4ht_sty_par` parameter. It can be set useing following command line call, for example:

     make4ht -f odt+odttemplate filename.tex "odttemplate=template.odt"



# Configuration file {#configfile}

It is possible to globally modify the build settings using the configuration
file. New compilation commands can be added, extensions can be loaded or
disabled and settings can be set.

## Location 

The configuration file can be saved either in
`$HOME/.config/make4ht/config.lua` or in `.make4ht` in the current directory or
it's parents (up to `$HOME`).

## Additional commands

There are two additional commands:

`Make:enable_extension(name)`

:  require extension

`Make:disable_extension(name)`

:  disable extension

## Example

The following configuration add support for the `biber` command, requires
`common_domfilters` extension and requires MathML
output for math.

    Make:add("biber", "biber ${input}")
    Make:enable_extension "common_domfilters"
    settings_add {
      tex4ht_sty_par =",mathml"
    }

# Command line options

    make4ht - build system for tex4ht
    Usage:
    make4ht [options] filename ["tex4ht.sty op." "tex4ht op." 
         "t4ht op" "latex op"]
    -b,--backend (default tex4ht) Backend used for xml generation.
         possible values: tex4ht or lua4ht
    -c,--config (default xhtml) Custom config file
    -d,--output-dir (default "")  Output directory
    -e,--build-file (default nil)  If build file name is different 
         than `filename`.mk4
    -f,--format  (default nil)  Output file format
    -l,--lua  Use lualatex for document compilation
    -m,--mode (default default) Switch which can be used in the makefile
    -n,--no-tex4ht  Disable dvi file processing with tex4ht command
    -s,--shell-escape Enables running external programs from LaTeX
    -u,--utf8  For output documents in utf8 encoding
    -v,--version  Print version number
    -x,--xetex Use xelatex for document compilation
    <filename> (string) Input file name


You can still invoke `make4ht` in the same way as `htlatex`:

    make4ht filename "customcfg, charset=utf-8" "-cunihtf -utf8" "-dfoo"

Note that this will not use `make4ht` routines for output directory making and
copying. If you want to use them, change the line above to:

    make4ht -d foo filename "customcfg, charset=utf-8" "-cunihtf -utf8"

This call has the same effect as the following:

    make4ht -u -c customcfg -d foo filename

Output directory doesn't have to exist, it will be created automatically. 
Specified path can be relative to current directory, or absolute:

    make4ht -d use/current/dir/ filename
    make4ht -d ../gotoparrentdir filename
    make4ht -d ~/gotohomedir filename
    make4ht -d c:\documents\windowspathsareworkingtoo filename

# Troubleshooting 

## Incorrect handling of command line arguments for `tex4ht`, `t4ht` or `latex`

Sometimes, you may get a similar error:

    make4ht:unrecognized parameter: i

It may be caused by a following `make4ht` invocation:

    make4ht hello.tex "customcfg,charset=utf-8" "-cunihtf -utf8" -d foo

The command line option parser is confused by mixing options for `make4ht` and
`tex4ht` in this case and tries to interpret the `-cunihtf -utf8`, which are
options for `tex4ht` command as `make4ht` options. To fix that, you can either
move the `-d foo` directly after `make4ht` command:

    make4ht -d foo hello.tex "customcfg,charset=utf-8" "-cunihtf -utf8"

Another option is to add a space before `tex4ht` options:

    make4ht hello.tex "customcfg,charset=utf-8" " -cunihtf -utf8" -d foo

The former way is preferable, though.

## Filenames containing spaces

`tex4ht` cannot handle filenames containing spaces. `make4ht` thus replaces spaces in input file names with underscores, so generated XML files use underscores instead of spaces as well.

## Filenames containing non-ASCII characters

The `odt` output doesn't support accented filenames, it is best to stick to ASCII characters in filenames.

# License

Permission is granted to copy, distribute and/or modify this software
under the terms of the LaTeX Project Public License, version 1.3.