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CHA-MAILCAP(5) File Formats Manual CHA-MAILCAP(5)

Mailcap

By default, Chawan’s buffers only handle HTML and plain text. The mailcap file can be used to view other file formats using external commands, or to convert them to HTML/plain text before displaying them in Chawan.

The browsecap file fulfills a similar purpose for URI scheme handling. Browsecap can override handling of any built-in scheme, or to add custom handlers (e.g. mutt(1) for mailto). When combined with cha-cgi(5), browsecap also enables extending Chawan with user-specified schemes.

(Browsecap is a more capable replacement for cha-urimethodmap(5); the latter is deprecated.)

Note that Chawan’s default mime.types file only recognizes a few file extensions, which may result in your entries not being executed if your system lacks an /etc/mime.types file. Please consult cha-mime.types(5) for details.

For an exact description of the mailcap format, see RFC 1524.

Browsecap is not standardized. The semantics are derived from w3mmee, but the two do not necessarily match in every aspect.

Search path

The search path for mailcap files is set by the configuration variable external.mailcap. This matches the recommended path in the RFC:

$HOME/.mailcap:/etc/mailcap:/usr/local/etc/mailcap

By default, mailcap entries are only executed if the user types r (run) after the prompt. Other options are to view the file with t (text), or to save the file with s.

If a capital letter is typed (e.g. shift + R), then a corresponding entry is appended to external.auto-mailcap (default: ~/.chawan/mailcap, or ~/.config/chawan/mailcap with XDG basedirs). (T)ext and (S)ave may also be used to append entries corresponding to the other display options.

Entries in auto-mailcap are automatically executed, so it is recommended to add your Chawan-specific entries there (or just set it to your personal mailcap file).

For browsecap, there is only an automatic variant so far, stored at external.auto-browsecap which defaults to ~/.chawan/browsecap (or ~/.config/chawan/browsecap with XDG basedirs).

Format

Chawan adheres to the format described in RFC 1524, with a few extensions.

text/html and text/plain entries are ignored, except when the entry includes an x-type parameter.

In browsecap, the MIME type field is treated as protocol/method. For example, http/get dispatches to GET requests to an HTTP scheme, ftp/post to POST requests to an FTP scheme, and https/* to all HTTPS schemes.

Templating

The command part of entries may include template strings which are substituted by the browser at execution.

Templates do not have to be quoted; Chawan quotes them automatically. (This works with $(command substitutions) as well.) However, other software may misbehave on such templates, so it may be better to assign them to a variable first, e.g.

text/x-example; s=%s cat "$s"; copiousoutput

Following templates are supported:

•
In mailcap, %s expands to the path. Specifying %s forces download of the external resource before the entry is executed. If %s is not specified, the resource is instead piped to standard input. (In this case, needsterminal does not apply.)

In browsecap, %s expands to the path segment of the URI instead.

•
In mailcap, %t expands to the content type. Named content type fields can also be specified with the syntax %{charset}. e.g. for text/html; charset=utf-8, %t expands to the entire string, and %{charset} expands to “utf-8”.

In browsecap, %t expands to protocol/method, where the method part is ASCII lower-cased. Named fields expand to URL search parameters, so for the URL https://example.org/search?q=blah, %{q} expands to “blah”.

•
Non-standard templates for the resource’s original URL: %u (from Netscape) expands to the original URL of the resource, %h and %p (from w3mmee) expands to the hostname and the port respectively, %H expands to the hostname and the port, and %? (from w3mmee) expands to the query string including the question mark.

(w3mmee did not actually include the question mark in %?, but this was changed in Chawan because the other design could not express the difference between the empty query string and the null query string.)

Fields

Following fields are recognized. (In browsecap, the x- prefix for extension fields is optional; in mailcap, it is mandatory.)

•
Entries with the test named field are only used if the test command exits with 0. For example, you can restrict entries that require X11 as follows:
image; feh -; test=test -n "$DISPLAY"

Note: entries with a test named field that include %s are skipped, and no data is piped into test commands. (The RFC does not specify how this should work, but the alternative behavior cannot be efficiently implemented in a browser.)

  • copiousoutput redirects the external command’s output into a new buffer. If either x-htmloutput or x-ansioutput is defined too, then copiousoutput is ignored.
  • needsterminal hands over control of the terminal to the command while it is running. It does nothing if one of copiousoutput, x-ansioutput, x-saveoutput or x-htmloutput is specified.
  • nametemplate provides a specific template for the temporary file created when %s is specified. See the RFC for details. This option has no effect in browsecap.
  • x-htmloutput (from w3m) behaves the same as copiousoutput, but makes Chawan interpret the command’s output as HTML.
  • x-ansioutput pipes the output through the “text/x-ansi” content type handler, so that ANSI colors, formatting, etc. are displayed correctly.
  • x-saveoutput prompts the user to save the entry’s output in a file.
  • x-needsstyle forces CSS to be processed for the specific type, even if styling is disabled in the config. Only useful when combined with x-htmloutput. (Also see the -cha-content-type media query in cha-css(7).)
  • x-needsimage forces images to be displayed in x-htmloutput, even if images are disabled.
  • x-type (from w3mmee) specifies a MIME type substitution. The command part is interpreted as a MIME type after template expansion, which is used instead of the original type. Such entries are only respected in external.auto-mailcap.

x-type applies even to text/plain and text/html documents (which are normally excluded from mailcap). However, x-type entries do not apply if the content type was forced (e.g. using the -T flag).

•
x-match (from w3mmee) restricts an entry’s URI to a full match of the specified regex. x-nc-match is the same, but it is case-insensitive. For example, x-match=https?://example\.org/.* restricts the entry to example.org (note the backslash).

When one of these fields is present together with test, the result is ANDed together.

Note: in w3mmee, x-match applied to URIs that substring-matched the regex; this has been changed in Chawan to a full match to reduce confusion. (For example, in w3mmee, a user could have mistaken example\.org for a regex that matches example.org, even though it would also match notexample.org. In Chawan, you’d have to use .*example\.org.* for this to happen.)

•
x-uri (from w3mmee) substitutes matching URIs with the URI specified inside the command field after template expansion. Like x-type, this does not execute a shell command. x-uri entries are only accepted in external.auto-browsecap.

After substitution, the user is redirected to the new URI.

•
x-resource must be used in combination with x-uri or x-cgioutput. Such entries also apply to requests initiated by a buffer, e.g. downloading CSS, IMG tags, etc.

When used in combination with x-uri, the latter’s semantics are changed to not redirect the user. So although another resource is fetched, the base URI remains the same. Further, entries preceding an entry with x-uri; x-resource are not considered after the redirection (unlike with x-uri, which restarts the request itself).

•
x-netpath (from w3mmee) restricts an entry to URIs which follow the net_path production of RFC 2396.

In practice, this means that the URI must start with two slashes and then follow with an authority (user, pass, host, port). For example, x-netpath matches proto://example.org/path, but not proto:/path.

The file scheme is special-cased such that it is never matched as net_path, even though it looks like one for legacy reasons.

  • x-internal (from w3mmee) marks an entry as “internal”. This means that it is impossible to navigate to this entry, or reach it from buffers through XMLHttpRequest, fetch, etc. In Chawan, it is used to implement image support; refer to cha-image(7) for details.
  • x-cgioutput is only accepted in external.auto-browsecap, and applies to all network requests. The command part is parsed as a subset of POSIX shell which accepts environment variables and parameters, but no shell substitution or variable substitution.

For example, following are valid cgioutput browsecap entries.

# /cgi-bin/ resolves to ~/.chawan/cgi-dir or ~/.config/chawan/cgi-dir
# (depending on where your config is)
example; url=%u /cgi-bin/path; cgioutput
example2; /cgi-bin/path %u; cgioutput

Mailcap examples

To automatically execute these entries, place them in ~/.chawan/mailcap (or ~/.config/chawan/mailcap if you use XDG basedirs). Alternatively, if you already have a mailcap file to share with other programs, you can set external.auto-mailcap to ~/.mailcap.

# Note: these examples require an entry in mime.types that sets e.g. md as
# the markdown content type.
# Handle markdown files using pandoc.
text/markdown; pandoc - -f markdown -t html -o -; x-htmloutput
# Show syntax highlighting for JavaScript source files using bat.
text/javascript; bat -f -l es6 --file-name %u -; x-ansioutput
# Play music using mpv, and hand over control of the terminal until mpv exits.
audio/*; mpv -; needsterminal
# Play videos using mpv in the background, redirecting its standard output
# and standard error to /dev/null.
video/*; mpv -
# Open docx files using LibreOffice Writer.
application/vnd.openxmlformats-officedocument.wordprocessingml.document; lowriter %s
# Display manpages using pandoc. (Make sure the mime type matches the one
# set in your mime.types file for extensions .1, .2, .3, ...)
application/x-troff-man; pandoc - -f man -t html -o -; x-htmloutput
# epub -> HTML using pandoc. (Again, don't forget to adjust mime.types.)
# We set http_proxy to keep it from downloading whatever through http/s.
application/epub+zip; http_proxy=localhost:0 pandoc - -f epub \
--embed-resources --standalone; x-htmloutput
# Hex viewer.  Usage: alias chadump='cha -Ttext/x-hexdump'
# (Uses GNU-specific flags, adjust as needed on other systems.)
text/x-hexdump; od -w12 -A x -t x1z -v; copiousoutput
# Following entry will be ignored, as text/html is supported natively by Chawan.
text/html; cha -dT text/html -I %{charset}; copiousoutput

Browsecap examples

Place these entries in ~/.chawan/browsecap (or ~/.config/chawan/browsecap if you use XDG basedirs).

# Use the `magnet.cgi' script to pass magnet links to Transmission.
# (`magnet.cgi' can be found in the `bonus/' directory.  You can also
# modify it to pass the links to your BitTorrent client of choice.)
# Since we are in browsecap, the `x-' prefix can be omitted.
magnet/*;	/cgi-bin/magnet.cgi?%u; cgioutput
# Open mailto: URIs using mutt.
# (This is the same as mailto/*; the trailing `/*' can be freely omitted.)
mailto;		mutt -- %s; needsterminal
# Open YouTube URLs with mpv.  (GET method only.)
# Like above, nc-match does not need the `x-' prefix because this is
# browsecap (not mailcap).
https/get;	mpv -- %u; needsterminal; nc-match=^https://(www\.)?youtube\.com/watch\?v=.*$

See also

cha(1)