werm: Web-based terminal multiplexer

werm is a terminal multiplexer and emulator empowered by browser tabs and your OS's desktop features.

TL;DR see screenshots

Usually we would use a terminal multiplexer to maintain sessions and manage multiple terminals remotely and even locally. So we cannot use any window manager and browser features to navigate and handle them.

More powerful terminals

But when your terminals are tabs, you can search them. When your terminals have URLs, you can open them with bookmarks. When your shells are first-class windows (and not panes in tmux or Screen), you can distribute them between multiple desktops and multiple monitors and snap or tile them in your display. You can even automate terminal actions and accelerate workflows with Javascript.

The purpose of werm is to expand those features you already use.

This is not an officially supported Google product.

FEATURES

• Ability to jump to different sessions using Ctrl+Shift+A (Chrome tab-search feature)

• Macros - Macros start with left or right alt and are a sequence of keys of arbitrary length. No chording is required when typing the macro activator sequence.

• Detachability (close the tab and the shell is still alive)

• Pixel-perfect bitmap fonts of various sizes which can even render on high-DPI screens without blur.

• Multiple shell profiles, each cloneable and initialized with its own command or rc file

• Profile name is in tab title so you can tab-search for it

• Most of what is in hterm (the engine for chromeOS SSH App and Crostini terminals)

• Works on any OS with a Chromium-based browser, including chromeOS and LaCros chromeOS

• Operate a terminal on your local machine or a remote one with a local browser.

• Shows active shell sessions and available profiles at http://localhost:<port>/attach. (This page can also be opened from a terminal with macros.)

• Overloaded decorator keys for easier coding and shell interaction: can type certain characters more easily

  • Done by pressing L/R shift keys, L/R ctrl keys, without chording with other keys; or the menu key
  • Look for deadkey_map or menu_key_inserts in index.html to customize the inserted characters.

• Keyboard layout remapping (search for remap_keys in index.html for an explanation)

Quickstart

Caveats

• chromeOS is the most thoroughly tested client OS at this time. Essential functionality has been confirmed for clients on Windows, macOS, and Linux.

• The Werm server, which is the local or remote machine running the terminals, only works on Linux for now.

• Chromium-based browsers are the most tested, but Firefox also appears to work. You should change ui.key.menuAccessKey or turn off ui.key.menuAccessKeyFocuses in about:config to prevent alt keys from being intercepted and use them for their intended purpose of activating macros.

Instructions

• Verify the following packages are installed:

  [Debian] libmd4c-dev libmd4c-html0-dev libssl-dev

  [Arch] core/make extra/md4c

• On your local or remote Linux machine, clone this repo to a convenient place and build. I recommend ~/.local/werm/src:

  $ mkdir -p ~/.local/werm
  $ cd ~/.local/werm
  $ git clone <repo_url> src
  $ cd src
  $ ./build
  

  ~/.local/werm/src, or wherever you choose to put the Werm source, is known as $WERMSRCDIR. This environment variable is available to all child processes of the server, including terminal sessions.

• Start the server.

  FOR THE WEB SERVER TO OPERATE THE LOCAL MACHINE

  Run: $ ./run spawner 127.0.0.1:8090

  Note that any logged in user will be able to start a shell as the user, since the port is accessible from localhost.

  This is sufficient for single-user machines. The opened port can be accessed in a local web browser or remotely with local ssh port forwarding:

  $ ssh ... -L 8090:werm-server:8090
  

  FOR THE WEB SERVER TO OPERATE A REMOTE MACHINE, or your local machine on which other users may log in, you should host the server on a Unix domain socket (UDS) so only one user has access:

  $ umask 0077
  $ ./run spawner [uds]:/tmp/werm.$USER.sock
  

  And then use port forwarding in your SSH command arguments (works with Chrome SSH extension, and any port number) to connect from your local machine:

  $ ssh ... -L 8090:/tmp/werm.<USER>.sock
  

• Open localhost:8090 in your browser to get an ephemeral shell. This will terminate the shell as soon as the tab is closed or the connection is lost.

• To open a persistent shell, use the localhost:8090/attach page. See ATTACH PAGE for details.

• Rather than use the attach page to reconnect to a shell, you can also re-open the URL e.g. with a bookmark or Ctrl+Shift+T.

• While any shell is open, type laH T to start a new persistent shell

How to read macro shortcuts

To understand macros cited in this guide, you will need to know how to activate them with the noted shortcut. Each shortcut is a plain string with an even number of characters (this is how they are expressed compactly in the source in long lists).

This syntax is also important in defining your own macros.

Each macro starts with either left alt or right alt (la and ra).

Each key is represented by two characters, called a mnemonic. Even if a key is a modifier such as alt, shift, or ctrl, there is no need to hold down the modifier.

Left and right modifiers of each kind are distinguished in the shortcut, so you have to press the right one. Here are the most common keys that are used in shortcuts:

• Capital letter followed by space, e.g. X or A indicates that alphabetic key.
• Number followed by a space is that number on the top row of the keyboard.
• Punctuation such as [ or , followed by a space is the non-numpad key which inserts that punction.
• Numpad keys are indicated by a # followed usually but not always by a numeric digit.
• la and ra are the alt keys, ls and rs are shift, and lc and rc are control.
• sp is the spacebar
• vs is backslash (vertical pipe) key (reVerse Solidus)

native_to_mn in index.html defines the complete mapping between mnemonics and the long-form name used by the JS Event API.

BASIC USE

• An ephemeral shell will terminate if you close the tab. You will create one simply by navigating to http://localhost:<port>/. To close an ephemeral shell, just use Ctrl+W or close the tab.

• A persistent shell stays alive even when the tab closes or the connection is lost. Terminate such a shell with Ctrl+D or the exit command before closing the tab.

• To add or remove macros, add it to the macro_map in index.html or a profile's JS code (see PROFILES).

  The left-hand side is the macro shortcut or mnemonic.

  The right-hand side is the string to enter or function to invoke. Use \r for return. Do not use shortcut mnemonics like es (escape) here, just the raw string.

• Fonts are changed with raF N ** where ** is A to J in roughly increasing size. E.g. press right-alt, F, N, A in sequence to choose the smallest font.

• Meta (i.e. super, apple on MacOS, search on ChromeOS) key is used in place of Alt for the terminal process. This is to allow Alt to be used for the start of macros. Note that on ChromeOS and e.g. Windows, meta pressed alone cannot be intercepted by Javascript, so meta is not used for macros.

Unconventional key mappings

Some common terminal key sequences are bound to browser operations, so alternate mappings are used to send the sequence to the terminal:

• Shift+Backspace to send Ctrl+W
  Ctrl+W closes the browser tab

• raT macro to send Ctrl+T
  Ctrl+T creates a new browser tab

• Shift+Enter to send Ctrl+N
  Ctrl+N creates a new browser window

ATTACH PAGE

Open the attach page by going to http://localhost:8090/attach, or using the rarsS T or rarsA T macros from within a terminal (see How to read macro shortcuts. The former shortcut uses a new tab (Separate) while the latter replaces the current tab.

From the attach page you can create or reconnect to persistent sessions.

• use a link in the "Existing" section to open an existing persisent session

• the list labeled "New" on the left side of /attach contains a line for every defined "profile." Any of these links will start a new session using that profile. To add a profile to get a particular workflow started, see PROFILES.

• The "New" list always starts with a "basic" link, which starts a profile of the empty name.

Existing session titles

Each existing session is shown with its title, which can be set explicitly with the set title macro raS T , invoked when the terminal is open, which locks the title to whatever text is on the current line. If the title is not set with that macro, or if it has been unset with laU T , then the title is the current line of text. If the alternative screen is open (such as with less or an editor) then the last line of text printed before entering the alternate screen is shown (for instance, $ vim foo.txt).

TERMINATE WERM

You can stop the server by opening the session titled ~spawner.<...> from /attach, and then pressing Ctrl+C to terminate it. Alternatively, you can use this command if you already have a terminal open:

$ pgrep -f Werm.prs..spawner | xargs kill

Terminals that are already open will continue to work, and these steps will not terminate any attached or detached terminal sessions.

SCROLLBACK

To access the scrollback buffer in a non-ephemeral shell, press laH L . This opens a new tab and runs less viewing the scrollback buffer. From there, you can close the scrollback viewer by simply closing the tab (it is an ephemeral session). If you quit less, then you will return to a shell. In this shell, the following commands and shell variables are available:

syntax	description
$logfile	the path of the scrollback file
lel	runs less $logfile (LEss Log)
rflt <args>	sends the lines in log in reverse order to sed <args>. For example, rflt '/$ grep/q; /\.h:/d' would recall the output of the just-run grep command but exclude matches found in C header files (Reverse FiLTer)
rfmt <args>	same as rflt, but while rflt pipes output through $PAGER, rfmt uses more
rft <args>	same as rflt but does not send to any pager
dl	runs cat $logfile (Dump Log)

These and other functions are defined in $WERMSRCDIR/util/logview

Scrollback features

• Open the scrollback in a new tab in an HTML <textarea> with macro laH M to get browser-native scrolling, searching, copying behavior. This does not use the alternate screen, but only the primary screen's scrollback, so you probably won't see editor or less content. This macro is defined in a tab with a terminal ID, but not an ephemeral terminal.

  • In the scrollback tab, to copy the selection, you may press Enter as an alternative to Ctrl+C followed by Ctrl+W.

• Show the visible text only in an HTML <textarea> with laH N . This works with editor and UI screens, unlike laH M . But everything else about its use is the same (Enter to copy text and close the tab).

• Scrollbacks are saved to disk in $WERMVARDIR/YEAR/MONTH/DAY, excluding any content printed to the alternate screen. You can turn off the scrollback feature and thereby prevent the logs from being written to disk by adding the sblvl= argument to $WERMFLAGS. The default value of sblvl is p which means plain scrollback logging is enabled. Setting sblvl to rp (e.g. export WERMFLAGS='sblvl=rp') would also turn on Raw logging, which saves the subprocess unified stdout/stderr streams (i.e. the raw bytes sent to the ptty) in files named *.raw.

Environment variables

WERMVARDIR

The environment variable $WERMVARDIR is the absolute path in which some long- term records and runtime files are kept. It defaults to $WERMSRCDIR/var. Set it before executing run.

WERMSOCKSDIR

The environment variable $WERMSOCKSDIR is the absolute path in which sockets for each session are stored. This does not affect the socket specified with [uds]:. It defaults to $WERMVARDIR/socks. Set it before executing run.

WERMFLAGS

The environment variable $WERMFLAGS is a URL query string without the leading question mark, e.g. foo=1&bar=2 or baz=3. If used, it must be set when starting the server, and the following values are supported:

flag name	value
dtachlog=	set to anything to enable detailed logging for the dtach component to /tmp/dtachlog.<pid> files
sblvl=	see SCROLLBACK FEATURES

PROFILES

A profile is meant to label and setup a starting state for a shell session. It can be used to quickly accomplish a certain task or prepare to enter a certain personalized workflow.

Profiles are divided into groups, and each profile has a name, an initialization command, and an optional list of Javascript files that the client will load, generally to just define macros, but also capable of modifying most pertinent variables in index.html.

Each profile group is defined by a single file in $WERMSRCDIR/profiles or $HOME/.config/werm/profiles. If $WERMPROFPATH is defined when running run, the paths in that are searched instead. To include more than one path in $WERMPROFPATH, separate separate them with a :.

The "group" feature is optional, meaning you may choose to put all of your profiles in a single group. Multiple groups are useful because the /attach page displays vertical space between each group. Multiple groups also allow you to define profiles across multiple files and directories.

The profile associated with a terminal ID is the portion of the terminal ID before the first ., or the entire terminal ID if there is no ..

Profile names may not contain the characters: %.+=&?\/" and space and tab.

A profile is defined by one line in its group file, and each line contains 1, 2, or 3 fields separated by a tab. Field one is the profile name. Field two is the preamble. Field three is the Javascript files to load with that profile, without the .js extension, separated by commas. Here is an example group file:

profile-foo<--TAB-->source ~/.foorc<--TAB-->foo-macros1,foo-macros2,common-macros
bar-profile<--TAB-->source ~/.barrc<--TAB-->bar-macros,common-macros
basic<--TAB-->source ~/.basicrc
no-preamble<--TAB--><--TAB-->common-macros
<--TAB--># basic<--TAB-->common

The first two profiles have all fields defined. The third profile has no extra JS to load, and the fourth profile has no preamble.

The fifth profile has no name. The empty-name profile is the basic profile, which always appears at the top of the New list in /attach. This is also the profile used for ephemeral sessions.

CUSTOM PROFILES: PREAMBLE

The preamble is typed automatically for you into the terminal when a new process has been started. If the preamble is not empty, a \n is automatically typed after it as well.

CUSTOM PROFILES: JAVASCRIPT

JS is loaded from directories listed in $WERMJSPATH, which is specified in the environment when running $WERMSRCDIR/run, and lists directories separated by colons, i.e. :

If $WERMJSPATH is not defined, it defaults to $WERMSRCDIR/js:$HOME/.config/werm/js

For instance, if the JS field of a profile is a,b,c, then Javascript will be loaded from any file named a.js, b.js, or c.js, in any directory in $WERMJSPATH. If the .js file is executable, it is executed and its stdout taken. Otherwise, the files contents are taken as-is.

For a given profile, each .js file is concatenated together and loaded as a single <script> element. To see the final .js file in use in a profile, open a terminal with the profile and enter the macro laO P J S . This will re-generate the .js file again and show it, rather than simply show what was really loaded and in effect for the page. (FIXME: this is not ideal)

The Javascript generally takes the form of extra macro maps put in the map at window.extended_macros, which look like the macro_map in index.html, e.g.:

$ cat foo.js
window.extended_macros.foo_macros = [
	['raD T ', 'third_party/dtach'],
	['raW S ', 'third_party/websocketd'],
];

$ cat bar.js
window.extended_macros.bar_macros = [
	...
];
show_barrier(80); /* Show marker after the 80th column, at page load. */

Setting the font

You can set the font either at page load or with a macro with:

/* Use the tiniest font by default. */
set_default_font(0);
window.extended_macros.font_macros = [
	/* Use a narrow font with a macro. */
	['laN A R R O W ', function() { set_font(3); }],
];

Where the argument is the zero-based index corresponding to the last letter used to activate it with the default macro. So to set the font corresponding to the raF N B macro, B is the identifying letter, so you would use set_font('B'.charCodeAt(0) - 65) or more simply set_font(1).

TERMINAL ID

When the process of a non-ephemeral terminal starts, it claims an ID of the form <profile_name>.<uniq_id>. The <profile_name> is empty for the basic profile. <uniq_id> is an ID which is designed be opaque but short and unique even among all profiles. This ID is used in log file names, browser tab names, and ps output for Werm-releated processes. The unique ID is a base 34 number matching the regex [a-z2-9]+ where the least significant digit is first, so typing .<two characters> is enough to identify the name out of all recently spawned terminals.

To reset the unique ID back to a single digit, delete the file that begins with $WERMVARDIR/nextterid. at any time.

CAPSLOCK SIMULATION AND AUTO-OFF

If you are using a Chromebook or have mapped your physical Caps Lock to something else, you can still get capslock functionality in Werm. This is done with the capsonwhile variable, which you set in a custom macro.

capsonwhile should be set to a regex which is compared against each pressed key's 2-char mnemonic. The first key that does not match will turn capslock off. For example,

window.extended_macros.caps_example = [
	['raC ', function() { capsonwhile = /[A-Z0-9] /; }],
];

This means that raC will turn on a simulated capslock until a non-alphabetic and non-numeric key is pressed. If you want to be able to type underscores and keep capslock on, you can keeps capslock on when shift or the dash/underscore key is pressed. That would be the regex /[A-Z0-9] |ls|rs|- /.

Alternatively, set capsonwhile to /../ to turn capslock on indefinitely (matches all keys) and set capsonwhile to 0 to turn it back off.

SUGGESTED UTILITIES

These are tools unaffiliated with Werm or Google which make Werm more powerful.

Tiling Window Manager for chromeOS

Available on the Chrome Webstore

Tiles a screen into more than two windows with the keyboard. You may not need this to only get two windows on the screen at one time.

In chromeOS without this extension, Alt+[ and Alt+] and Meta+Alt+M are sufficient to get two windows per monitor, on any attached monitor.

New tab redirect

Available on the Chrome webstore

Opens an ephemeral terminal in a new tab (see also pass_ctrl_L in index.html for easier access to address bar in new tabs)