| urxvt(1) | RXVT-UNICODE | urxvt(1) |
rxvt-unicode - (ouR XVT, unicode), a VT102 emulator for the X window system
urxvt [options] [-e command [ args ]]
rxvt-unicode, version 9.30, is a colour vt102 terminal emulator intended as an xterm(1) replacement for users who do not require features such as Tektronix 4014 emulation and toolkit-style configurability. As a result, rxvt-unicode uses much less swap space -- a significant advantage on a machine serving many X sessions.
This document is also available on the World-Wide-Web at <http://pod.tst.eu/http://cvs.schmorp.de/rxvt-unicode/doc/rxvt.1.pod>.
See urxvt(7) (try "man 7 urxvt") for a list of frequently asked questions and answer to them and some common problems. That document is also accessible on the World-Wide-Web at <http://pod.tst.eu/http://cvs.schmorp.de/rxvt-unicode/doc/rxvt.7.pod>.
Unlike the original rxvt, rxvt-unicode stores all text in Unicode internally. That means it can store and display most scripts in the world. Being a terminal emulator, however, some things are very difficult, especially cursive scripts such as arabic, vertically written scripts like mongolian or scripts requiring extremely complex combining rules, like tibetan or devanagari. Don't expect pretty output when using these scripts. Most other scripts, latin, cyrillic, kanji, thai etc. should work fine, though. A somewhat difficult case are right-to-left scripts, such as hebrew: rxvt-unicode adopts the view that bidirectional algorithms belong in the application, not the terminal emulator (too many things -- such as cursor-movement while editing -- break otherwise), but that might change.
If you are looking for a terminal that supports more exotic scripts, let me recommend "mlterm", which is a very user friendly, lean and clean terminal emulator. In fact, the reason rxvt-unicode was born was solely because the author couldn't get "mlterm" to use one font for latin1 and another for japanese.
Therefore another design rationale was the use of multiple fonts to display characters: The idea of a single unicode font which many other programs force onto its users never made sense to me: You should be able to choose any font for any script freely.
Apart from that, rxvt-unicode is also much better internationalised than its predecessor, supports things such as XFT and ISO 14755 that are handy in i18n-environments, is faster, and has a lot bugs less than the original rxvt. This all in addition to dozens of other small improvements.
It is still faithfully following the original rxvt idea of being lean and nice on resources: for example, you can still configure rxvt-unicode without most of its features to get a lean binary. It also comes with a client/daemon pair that lets you open any number of terminal windows from within a single process, which makes startup time very fast and drastically reduces memory usage. See urxvtd(1) (daemon) and urxvtc(1) (client).
It also makes technical information about escape sequences (which have been extended) more accessible: see urxvt(7) for technical reference documentation (escape sequences etc.).
The urxvt options (mostly a subset of xterm's) are listed below. In keeping with the smaller-is-better philosophy, options may be eliminated or default values chosen at compile-time, so options and defaults listed may not accurately reflect the version installed on your system. `urxvt -h' gives a list of major compile-time options on the Options line. Option descriptions may be prefixed with which compile option each is dependent upon. e.g. `Compile XIM:' requires XIM on the Options line. Note: `urxvt -help' gives a list of all command-line options compiled into your version.
Note that urxvt permits the resource name to be used as a long-option (--/++ option) so the potential command-line options are far greater than those listed. For example: `urxvt --loginShell --color1 Orange'.
The following options are available:
[Please note that many X servers (and libXft) are buggy with respect to "-depth 32" and/or alpha channels, and will cause all sorts of graphical corruption. This is harmless, but we can't do anything about this, so watch out]
In short, to specify an X11 core font, just specify its name or prefix it with "x:". To specify an XFT-font, you need to prefix it with "xft:", e.g.:
urxvt -fn "xft:Bitstream Vera Sans Mono:pixelsize=15"
urxvt -fn "9x15bold,xft:Bitstream Vera Sans Mono"
See also the question "How does rxvt-unicode choose fonts?" in the FAQ section of urxvt(7).
Please note that you must specify a program with arguments. If you want to run shell commands, you have to specify the shell, like this:
urxvt -e sh -c "shell commands"
If the perl extension "xim-onthespot" is used (which is the default), then additionally the "OnTheSpot" preedit type is available.
Note that you need to use the same syntax as in the .Xdefaults file, e.g. "*.background: black". Also note that all urxvt-specific options can be specified as long-options on the commandline, so use of -xrm is mostly limited to cases where you want to specify other resources (e.g. for input methods) or for compatibility with other programs.
Right now, urxvt will first unmap/map the specified window, so it shouldn't be a top-level window. urxvt will also reconfigure it quite a bit, so don't expect it to keep some specific state. It's best to create an extra subwindow for urxvt and leave it alone.
The window will not be destroyed when urxvt exits.
It might be useful to know that urxvt will not close file descriptors passed to it (except for stdin/out/err, of course), so you can use file descriptors to communicate with the programs within the terminal. This works regardless of whether the "-embed" option was used or not.
Here is a short Gtk2-perl snippet that illustrates how this option can be used (a longer example is in doc/embed):
my $rxvt = new Gtk2::Socket;
$rxvt->signal_connect_after (realize => sub {
my $xid = $_[0]->window->get_xid;
system "urxvt -embed $xid &";
});
If this switch is given, urxvt will not create any utmp/wtmp entries and will not tinker with pty/tty permissions - you have to do that yourself if you want that.
As an extremely special case, specifying "-1" will completely suppress pty/tty operations, which is probably only useful in conjunction with some perl extension that manages the terminal.
Here is a example in perl that illustrates how this option can be used (a longer example is in doc/pty-fd):
use IO::Pty;
use Fcntl;
my $pty = new IO::Pty;
fcntl $pty, F_SETFD, 0; # clear close-on-exec
system "urxvt -pty-fd " . (fileno $pty) . "&";
close $pty;
# now communicate with rxvt
my $slave = $pty->slave;
while (<$slave>) { print $slave "got <$_>\n" }
Note that, despite what the name might imply, the file descriptor does not need to be a pty, it can be a bi-directional pipe as well (e.g. a unix domain or tcp socket). While tty operations cannot be done in this case, urxvt can still be remote controlled with it:
use Socket;
use Fcntl;
socketpair my $URXVT, my $slave, Socket::AF_UNIX, Socket::SOCK_STREAM, Socket::PF_UNSPEC;
fcntl $slave, Fcntl::F_SETFD, 0;
system "exec urxvt -pty-fd " . (fileno $slave) . " &";
close $slave;
syswrite $URXVT, "Type a secret password: ";
my $secret = do { local $/ = "\r"; <$URXVT> };
print "Not so secret anymore: $secret\n";
Note: `urxvt --help' gives a list of all resources (long options) compiled into your version. All resources are also available as long-options.
You can set and change the resources using X11 tools like xrdb. Many distribution do also load settings from the ~/.Xresources file when X starts. urxvt will consult the following files/resources in order, with later settings overwriting earlier ones:
1. app-defaults file in $XAPPLRESDIR 2. $HOME/.Xdefaults 3. RESOURCE_MANAGER property on root-window of screen 0 4. SCREEN_RESOURCES property on root-window of the current screen 5. $XENVIRONMENT file OR $HOME/.Xdefaults-<nodename> 6. resources specified via -xrm on the commandline
Note that when reading X resources, urxvt recognizes two class names: Rxvt and URxvt. The class name Rxvt allows resources common to both urxvt and the original rxvt to be easily configured, while the class name URxvt allows resources unique to urxvt, to be shared between different urxvt configurations. If no resources are specified, suitable defaults will be used. Command-line arguments can be used to override resource settings. The following resources are supported (you might want to check the urxvtperl(3) manpage for additional settings by perl extensions not documented here):
Colours higher than 15 cannot be set using resources (yet), but can be changed using an escape command (see urxvt(7)).
Colours 16-79 form a standard 4x4x4 colour cube (the same as xterm with 88 colour support). Colours 80-87 are evenly spaces grey steps.
False: specify that smooth scrolling should be used. urxvt will force a screen refresh on each new line it received; option +j.
False: specify that everything is to be displayed, even if the refresh is too fast for the human eye to read anything (or the monitor to display anything); option +ss.
Each font can either be a standard X11 core font (XLFD) name, with optional prefix "x:" or a Xft font (Compile xft), prefixed with "xft:".
In addition, each font can be prefixed with additional hints and specifications enclosed in square brackets ("[]"). The only available hint currently is "codeset=codeset-name", and this is only used for Xft fonts.
For example, this font resource
URxvt.font: 9x15bold,\
-misc-fixed-bold-r-normal--15-140-75-75-c-90-iso10646-1,\
-misc-fixed-medium-r-normal--15-140-75-75-c-90-iso10646-1, \
[codeset=JISX0208]xft:Kochi Gothic:antialias=false, \
xft:Code2000:antialias=false
specifies five fonts to be used. The first one is "9x15bold" (actually the iso8859-1 version of the second font), which is the base font (because it is named first) and thus defines the character cell grid to be 9 pixels wide and 15 pixels high.
The second font is just used to add additional unicode characters not in the base font, likewise the third, which is unfortunately non-bold, but the bold version of the font does contain fewer characters, so this is a useful supplement.
The third font is an Xft font with aliasing turned off, and the characters are limited to the JIS 0208 codeset (i.e. japanese kanji). The font contains other characters, but we are not interested in them.
The last font is a useful catch-all font that supplies most of the remaining unicode characters.
If specified and non-empty, then the syntax is the same as for the font-resource, and the given font list will be used as is, which makes it possible to substitute completely different font styles for bold and italic.
If unset (the default), a suitable font list will be synthesized by "morphing" the normal text font list into the desired shape. If that is not possible, replacement fonts of the desired shape will be tried.
If set, but empty, then this specific style is disabled and the normal text font will being used for the given style.
urxvt resets the urgency hint on every focus change.
The string will be interpreted as if typed into the shell as-is.
Example:
URxvt.print-pipe: cat > $(TMPDIR=$HOME mktemp urxvt.XXXXXX)
This creates a new file in your home directory with the screen contents every time you hit "Print".
When the perl selection extension is in use (the default if compiled in, see the urxvtperl(3) manpage), a suitable regex using these characters will be created (if the resource exists, otherwise, no regex will be created). In this mode, characters outside ISO-8859-1 can be used.
When the selection extension is not used, only ISO-8859-1 characters can be used. If not specified, the built-in default is used:
BACKSLASH `"'&()*,;<=>?@[]^{|}
You can enable them by setting this boolean resource or specifying -insecure as an option. At the moment, this enables display-answer, locale, findfont, icon label and window title requests.
Using this resource, you can map key combinations such as "Ctrl-Shift-BackSpace" to various actions, such as outputting a different string than would normally result from that combination, making the terminal scroll up or down the way you want it, or any other thing an extension might provide.
The key combination that triggers the action, sym, has the following format:
(modifiers-)key
Where modifiers can be any combination of the following full or abbreviated modifier names:
| ISOLevel3 | I |
| AppKeypad | K |
| Control | C |
| NumLock | N |
| Shift | S |
| Meta | M or A |
| Lock | L |
| Mod1 | 1 |
| Mod2 | 2 |
| Mod3 | 3 |
| Mod4 | 4 |
| Mod5 | 5 |
The NumLock, Meta and ISOLevel3 modifiers are usually aliased to whatever modifier the NumLock key, Meta/Alt keys or ISO Level3 Shift/AltGr keys are being mapped. AppKeypad is a synthetic modifier mapped to the current application keymap mode state.
Due the the large number of modifier combinations, a key mapping will match if at least the specified identifiers are being set, and no other key mappings with those and more bits are being defined. That means that defining a mapping for "a" will automatically provide definitions for "Meta-a", "Shift-a" and so on, unless some of those are defined mappings themselves. See the "builtin:" action, below, for a way to work around this when this is a problem.
The spelling of key depends on your implementation of X. An easy way to find a key name is to use the xev(1) command. You can find a list by looking for the "XK_" macros in the X11/keysymdef.h include file (omit the "XK_" prefix). Alternatively you can specify key by its hex keysym value (0x0000 - 0xFFFF).
As with any resource value, the action string may contain backslash escape sequences ("\n": newline, "\\": backslash, "\000": octal number), see RESOURCES in "man 7 X" for further details.
An action starts with an action prefix that selects a certain type of action, followed by a colon. An action string without colons is interpreted as a literal string to pass to the tty (as if it was prefixed with "string:").
The following action prefixes are known - extensions can provide additional prefixes:
URxvt.keysym.Shift-Tab: string:echo rm -rf /\n
This could in theory be used to completely redefine your keymap.
In addition, for actions of this type, you can define a range of keysyms in one shot by loading the "keysym-list" perl extension and providing an action with pattern list/PREFIX/MIDDLE/SUFFIX, where the delimiter `/' should be a character not used by the strings.
Its usage can be demonstrated by an example:
URxvt.keysym.M-C-0x61: list|\033<|abc|>
The above line is equivalent to the following three lines:
URxvt.keysym.Meta-Control-0x61: string:\033<a>
URxvt.keysym.Meta-Control-0x62: string:\033<b>
URxvt.keysym.Meta-Control-0x63: string:\033<c>
For example the following means "change the current locale to "zh_CN.GBK" when Control-Meta-c is being pressed":
URxvt.keysym.M-C-c: command:\033]701;zh_CN.GBK\007
The following example will map Control-Meta-1 and Control-Meta-2 to the fonts "suxuseuro" and "9x15bold", so you can have some limited font-switching at runtime:
URxvt.keysym.M-C-1: command:\033]50;suxuseuro\007
URxvt.keysym.M-C-2: command:\033]50;9x15bold\007
Other things are possible, e.g. resizing (see urxvt(7) for more info):
URxvt.keysym.M-C-3: command:\033[8;25;80t
URxvt.keysym.M-C-4: command:\033[8;48;110t
For example if you overwrite the "Insert" key you will disable urxvt's "Shift-Insert" mapping. To re-enable that, you can poke "holes" into the user-defined keymap using the "builtin:" replacement:
URxvt.keysym.Insert: <my insert key sequence>
URxvt.keysym.S-Insert: builtin:
The first line defines a mapping for "Insert" and any combination of modifiers. The second line re-establishes the default mapping for "Shift-Insert".
An example might make it clearer: urxvt normally pastes the selection when you press "Shift-Insert". With the following bindings, it would instead emit the (undocumented, but what applications running in the terminal might expect) sequence "ESC [ 2 $" instead:
URxvt.keysym.S-Insert: builtin-string:
URxvt.keysym.C-S-Insert: builtin:
The first line disables the paste functionality for that key combination, and the second reinstates the default behaviour for "Control-Shift-Insert", which would otherwise be overridden.
Similarly, to let applications gain access to the "C-M-c" (copy to clipboard) and "C-M-v" (paste clipboard) key combination, you can do this:
URxvt.keysym.C-M-c: builtin-string:
URxvt.keysym.C-M-v: builtin-string:
Not all extensions define actions, but popular extensions that do include the selection and matcher extensions (documented in their own manpages, urxvt-selection(1) and urxvt-matcher(1), respectively).
From the silly examples department, this will rot13-"encrypt" urxvt's selection when Alt-Control-c is pressed on typical PC keyboards:
URxvt.keysym.M-C-c: selection:rot13
Extension names can be prefixed with a "-" sign to remove them again, in case they had been specified earlier. This can be useful to selectively disable some extensions loaded by default, or specified via the "perl-ext-common" resource. For example, "default,-selection" will use all the default extensions except "selection".
To prohibit autoloading of extensions, you can prefix them with "/", which will make urxvt refuse to automatically load them (this can be overridden, however, by specifying the extension name again without a prefix, though). This does not prohibit extensions themselves loading other extensions. For example, "default,/background" will keep the "background" extension from being loaded when a background OSC sequence is received.
The default set includes the "selection", "option-popup", "selection-popup", "readline", "searchable-scrollback" and "confirm-paste" extensions, as well as any extensions which are mentioned in keysym resources.
Any extension such that a corresponding resource is given on the command line is automatically appended to perl-ext.
Each extension is looked up in the library directories, loaded if necessary, and bound to the current terminal instance. When the library search path contains multiple extension files of the same name, then the first one found will be used.
If both of these resources are the empty string, then the perl interpreter will not be initialized. The rationale for having two options is that perl-ext-common will be used for extensions that should be available to all instances, while perl-ext is used for specific instances.
See the urxvtperl(3) manpage.
URxvt.keysym.M-s: searchable-scrollback:start
Lines of text that scroll off the top of the urxvt window (resource: saveLines) and can be scrolled back using the scrollbar or by keystrokes. The normal urxvt scrollbar has arrows and its behaviour is fairly intuitive. The xterm-scrollbar is without arrows and its behaviour mimics that of xterm
Scroll down with Button1 (xterm-scrollbar) or Shift-Next. Scroll up with Button3 (xterm-scrollbar) or Shift-Prior. Continuous scroll with Button2.
To temporarily override mouse reporting, for either the scrollbar or the normal text selection/insertion, hold either the Shift or the Meta (Alt) key while performing the desired mouse action.
If mouse reporting mode is active, the normal scrollbar actions are disabled -- on the assumption that we are using a fullscreen application. Instead, pressing Button1 and Button3 sends ESC [ 6 ~ (Next) and ESC [ 5 ~ (Prior), respectively. Similarly, clicking on the up and down arrows sends ESC [ A (Up) and ESC [ B (Down), respectively.
The behaviour of text selection and insertion/pasting mechanism is similar to xterm(1).
Starting a selection while pressing the Meta key (or Meta+Ctrl keys) (Compile: frills) will create a rectangular selection instead of a normal one. In this mode, every selected row becomes its own line in the selection, and trailing whitespace is visually underlined and removed from the selection.
Pressing Shift-Insert causes the value of the PRIMARY selection to be inserted too.
rxvt-unicode also provides the bindings Ctrl-Meta-c and <Ctrl-Meta-v> to interact with the CLIPBOARD selection. The first binding causes the value of the internal selection to be copied to the CLIPBOARD selection, while the second binding causes the value of the CLIPBOARD selection to be inserted.
Changing fonts (or font sizes, respectively) via the keypad is not yet supported in rxvt-unicode. Bug me if you need this.
You can, however, switch fonts at runtime using escape sequences, e.g.:
printf '\e]710;%s\007' "9x15bold,xft:Kochi Gothic"
You can use keyboard shortcuts, too:
URxvt.keysym.M-C-1: command:\033]710;suxuseuro\007\033]711;suxuseuro\007 URxvt.keysym.M-C-2: command:\033]710;9x15bold\007\033]711;9x15bold\007
rxvt-unicode will automatically re-apply these fonts to the output so far.
ISO 14755 is a standard for entering and viewing unicode characters and character codes using the keyboard. It consists of 4 parts. The first part is available if rxvt-unicode has been compiled with "--enable-frills", the rest is available when rxvt-unicode was compiled with "--enable-iso14755".
This allows you to enter unicode characters using their hexcode.
Start by pressing and holding both "Control" and "Shift", then enter hex-digits (between one and six). Releasing "Control" and "Shift" will commit the character as if it were typed directly. While holding down "Control" and "Shift" you can also enter multiple characters by pressing "Space", which will commit the current character and lets you start a new one.
As an example of use, imagine a business card with a japanese e-mail address, which you cannot type. Fortunately, the card has the e-mail address printed as hexcodes, e.g. "671d 65e5". You can enter this easily by pressing "Control" and "Shift", followed by "6-7-1-D-SPACE-6-5-E-5", followed by releasing the modifier keys.
This mode lets you input characters representing the keycap symbols of your keyboard, if representable in the current locale encoding.
Start by pressing "Control" and "Shift" together, then releasing them. The next special key (cursor keys, home etc.) you enter will not invoke its usual function but instead will insert the corresponding keycap symbol. The symbol will only be entered when the key has been released, otherwise pressing e.g. "Shift" would enter the symbol for "ISO Level 2 Switch", although your intention might have been to enter a reverse tab (Shift-Tab).
While this is implemented already (it's basically the selection mechanism), it could be extended by displaying a unicode character map.
This method lets you display the unicode character code associated with characters already displayed.
You enter this mode by holding down "Control" and "Shift" together, then pressing and holding the left mouse button and moving around. The unicode hex code(s) (it might be a combining character) of the character under the pointer is displayed until you release "Control" and "Shift".
In addition to the hex codes it will display the font used to draw this character - due to implementation reasons, characters combined with combining characters, line drawing characters and unknown characters will always be drawn using the built-in support font.
With respect to conformance, rxvt-unicode is supposed to be compliant to both scenario A and B of ISO 14755, including part 5.2.
urxvt tries to write an entry into the utmp(5) file so that it can be seen via the who(1) command, and can accept messages. To allow this feature, urxvt may need to be installed setuid root on some systems or setgid to root or to some other group on others.
In addition to the default foreground and background colours, urxvt can display up to 88/256 colours: 8 ANSI colours plus high-intensity (potentially bold/blink) versions of the same, and 72 (or 240 in 256 colour mode) colours arranged in an 4x4x4 (or 6x6x6) colour RGB cube plus a 8 (24) colour greyscale ramp.
urxvt supports direct 24-bit fg/bg RGB colour escapes " ESC [ 38 ; 2 ; R ; G ; Bm " / " ESC [ 48 ; 2; R ; G ; Bm ". However the number of 24-bit colours that can be used is limited: an internal 7x7x5 (256 colour mode) or 6x6x4 (88 colour mode) colour cube is used to index into the 24-bit colour space. When indexing collisions happen, the nearest old colour in the cube will be adapted to the new 24-bit RGB colour. That means one cannot use many similar 24-bit colours. It's typically not a problem in common scenarios.
Here is a list of the ANSI colours with their names.
| color0 | (black) | = Black |
| color1 | (red) | = Red3 |
| color2 | (green) | = Green3 |
| color3 | (yellow) | = Yellow3 |
| color4 | (blue) | = Blue3 |
| color5 | (magenta) | = Magenta3 |
| color6 | (cyan) | = Cyan3 |
| color7 | (white) | = AntiqueWhite |
| color8 | (bright black) | = Grey25 |
| color9 | (bright red) | = Red |
| color10 | (bright green) | = Green |
| color11 | (bright yellow) | = Yellow |
| color12 | (bright blue) | = Blue |
| color13 | (bright magenta) | = Magenta |
| color14 | (bright cyan) | = Cyan |
| color15 | (bright white) | = White |
| foreground | = Black | |
| background | = White |
It is also possible to specify the colour values of foreground, background, cursorColor, cursorColor2, colorBD, colorUL as a number 0-15, as a convenient shorthand to reference the colour name of color0-color15.
The following text gives values for the standard 88 colour mode (and values for the 256 colour mode in parentheses).
The RGB cube uses indices 16..79 (16..231) using the following formulas:
index_88 = (r * 4 + g) * 4 + b + 16 # r, g, b = 0..3 index_256 = (r * 6 + g) * 6 + b + 16 # r, g, b = 0..5
The grayscale ramp uses indices 80..87 (232..239), from 10% to 90% in 10% steps (1/26 to 25/26 in 1/26 steps) - black and white are already part of the RGB cube.
Together, all those colours implement the 88 (256) colour xterm colours. Only the first 16 can be changed using resources currently, the rest can only be changed via command sequences ("escape codes").
Applications are advised to use terminfo or command sequences to discover number and RGB values of all colours (yes, you can query this...).
Note that -rv ("reverseVideo: True") simulates reverse video by always swapping the foreground/background colours. This is in contrast to xterm(1) where the colours are only swapped if they have not otherwise been specified. For example,
urxvt -fg Black -bg White -rv
would yield White on Black, while on xterm(1) it would yield Black on White.
If Xft support has been compiled in and as long as Xft/Xrender/X don't get their act together, rxvt-unicode will do its own alpha channel management:
You can prefix any colour with an opaqueness percentage enclosed in brackets, i.e. "[percent]", where "percent" is a decimal percentage (0-100) that specifies the opacity of the colour, where 0 is completely transparent and 100 is completely opaque. For example, "[50]red" is a half-transparent red, while "[95]#00ff00" is an almost opaque green. This is the recommended format to specify transparency values, and works with all ways to specify a colour.
For complete control, rxvt-unicode also supports "rgba:rrrr/gggg/bbbb/aaaa" (exactly four hex digits/component) colour specifications, where the additional "aaaa" component specifies opacity (alpha) values. The minimum value of 0000 is completely transparent, while "ffff" is completely opaque). The two example colours from earlier could also be specified as "rgba:ff00/0000/0000/8000" and "rgba:0000/ff00/0000/f332".
You probably need to specify "-depth 32", too, to force a visual with alpha channels, and have the luck that your X-server uses ARGB pixel layout, as X is far from just supporting ARGB visuals out of the box, and rxvt-unicode just fudges around.
For example, the following selects an almost completely transparent black background, and an almost opaque pink foreground:
urxvt -depth 32 -bg rgba:0000/0000/0000/4444 -fg "[80]pink"
When not using a background image, then the interpretation of the alpha channel is up to your compositing manager (most interpret it as transparency of course).
When using a background pixmap or pseudo-transparency, then the background colour will always behave as if it were completely transparent (so the background image shows instead), regardless of how it was specified, while other colours will either be transparent as specified (the background image will show through) on servers supporting the RENDER extension, or fully opaque on servers not supporting the RENDER EXTENSION.
Please note that due to bugs in Xft, specifying alpha values might result in garbage being displayed when the X-server does not support the RENDER extension.
urxvt sets and/or uses the following environment variables:
Default $HOME/.urxvt/urxvtd-<nodename>.
urxvt(7), urxvtc(1), urxvtd(1), urxvt-extensions(1), urxvtperl(3), xterm(1), sh(1), resize(1), X(1), pty(4), tty(4), utmp(5)
<http://software.schmorp.de/pkg/rxvt-unicode.html>
Project Coordinator (changes.txt 2.11 to 2.21)
Project Coordinator (changes.txt 2.4.6 - rxvt-unicode)
Project Coordinator (Changes 1.0 -)
| 2023-03-23 | 9.30 |