It almost works, but few issues.

[rosso-]

I'm using urxvt.

So, after issuing this:

(require 'term-keys-urxvt)
(with-temp-buffer
(insert (term-keys/urxvt-xresources))
(append-to-file (point-min) (point-max) "~/.Xresources"))

I ran xrdb -merge ~/.Xresources

And got such output:

/home/user/.Xresources:60:29: warning: missing terminating '"' character [-Winvalid-pp-token]
   60 | URxvt.keysym.C-2: string:<U+001B><U+001F>,"<U+001F>
      |                                           ^
/home/user/.Xresources:63:34: warning: missing terminating ' character [-Winvalid-pp-token]
   63 | URxvt.keysym.S-C-1-at: string:<U+001B><U+001F>,'<U+001F>
      |                                                ^
/home/user/.Xresources:72:29: warning: missing terminating '"' character [-Winvalid-pp-token]
   72 | URxvt.keysym.C-5: string:<U+001B><U+001F>."<U+001F>
      |                                           ^
/home/user/.Xresources:75:39: warning: missing terminating ' character [-Winvalid-pp-token]
   75 | URxvt.keysym.S-C-1-percent: string:<U+001B><U+001F>.'<U+001F>
      |                                                     ^
/home/user/.Xresources:84:29: warning: missing terminating '"' character [-Winvalid-pp-token]
   84 | URxvt.keysym.C-8: string:<U+001B><U+001F>0"<U+001F>
      |                                           ^
/home/user/.Xresources:87:40: warning: missing terminating ' character [-Winvalid-pp-token]
   87 | URxvt.keysym.S-C-1-asterisk: string:<U+001B><U+001F>0'<U+001F>
      |                                                      ^
/home/user/.Xresources:96:33: warning: missing terminating '"' character [-Winvalid-pp-token]
   96 | URxvt.keysym.C-minus: string:<U+001B><U+001F>2"<U+001F>
      |                                               ^
/home/user/.Xresources:99:42: warning: missing terminating ' character [-Winvalid-pp-token]
   99 | URxvt.keysym.S-C-1-underscore: string:<U+001B><U+001F>2'<U+001F>
      |                                                        ^
/home/user/.Xresources:110:31: warning: missing terminating '"' character [-Winvalid-pp-token]
  110 | URxvt.keysym.C-Tab: string:<U+001B><U+001F>4"<U+001F>
      |                                             ^
/home/user/.Xresources:113:44: warning: missing terminating ' character [-Winvalid-pp-token]
  113 | URxvt.keysym.S-C-1-ISO_Left_Tab: string:<U+001B><U+001F>4'<U+001F>
      |                                                          ^
/home/user/.Xresources:119:33: warning: missing terminating ' character [-Winvalid-pp-token]
  119 | URxvt.keysym.S-C-1-E: string:<U+001B><U+001F>6'<U+001F>
      |                                               ^
/home/user/.Xresources:125:33: warning: missing terminating ' character [-Winvalid-pp-token]
  125 | URxvt.keysym.S-C-1-Y: string:<U+001B><U+001F>8'<U+001F>
      |                                               ^
/home/user/.Xresources:131:33: warning: missing terminating ' character [-Winvalid-pp-token]
  131 | URxvt.keysym.S-C-1-O: string:<U+001B><U+001F>:'<U+001F>
      |                                               ^
/home/user/.Xresources:138:40: warning: missing terminating '"' character [-Winvalid-pp-token]
  138 | URxvt.keysym.C-bracketright: string:<U+001B><U+001F><"<U+001F>
      |                                                      ^
/home/user/.Xresources:141:42: warning: missing terminating ' character [-Winvalid-pp-token]
  141 | URxvt.keysym.S-C-1-braceright: string:<U+001B><U+001F><'<U+001F>
      |                                                        ^
/home/user/.Xresources:149:33: warning: missing terminating ' character [-Winvalid-pp-token]
  149 | URxvt.keysym.S-C-1-A: string:<U+001B><U+001F>>'<U+001F>
      |                                               ^
/home/user/.Xresources:155:33: warning: missing terminating ' character [-Winvalid-pp-token]
  155 | URxvt.keysym.S-C-1-F: string:<U+001B><U+001F>@'<U+001F>
      |                                               ^
/home/user/.Xresources:162:33: warning: missing terminating ' character [-Winvalid-pp-token]
  162 | URxvt.keysym.S-C-1-J: string:<U+001B><U+001F>B'<U+001F>
      |                                               ^
/home/user/.Xresources:167:37: warning: missing terminating '"' character [-Winvalid-pp-token]
  167 | URxvt.keysym.C-semicolon: string:<U+001B><U+001F>D"<U+001F>
      |                                                   ^
/home/user/.Xresources:170:37: warning: missing terminating ' character [-Winvalid-pp-token]
  170 | URxvt.keysym.S-C-1-colon: string:<U+001B><U+001F>D'<U+001F>
      |                                                   ^
/home/user/.Xresources:175:37: warning: missing terminating '"' character [-Winvalid-pp-token]
  175 | URxvt.keysym.C-backslash: string:<U+001B><U+001F>F"<U+001F>
      |                                                   ^
/home/user/.Xresources:178:35: warning: missing terminating ' character [-Winvalid-pp-token]
  178 | URxvt.keysym.S-C-1-bar: string:<U+001B><U+001F>F'<U+001F>
      |                                                 ^
/home/user/.Xresources:184:33: warning: missing terminating ' character [-Winvalid-pp-token]
  184 | URxvt.keysym.S-C-1-C: string:<U+001B><U+001F>H'<U+001F>
      |                                               ^
/home/user/.Xresources:190:33: warning: missing terminating ' character [-Winvalid-pp-token]
  190 | URxvt.keysym.S-C-1-N: string:<U+001B><U+001F>J'<U+001F>
      |                                               ^
/home/user/.Xresources:197:33: warning: missing terminating '"' character [-Winvalid-pp-token]
  197 | URxvt.keysym.C-period: string:<U+001B><U+001F>L"<U+001F>
      |                                               ^
/home/user/.Xresources:200:38: warning: missing terminating ' character [-Winvalid-pp-token]
  200 | URxvt.keysym.S-C-1-greater: string:<U+001B><U+001F>L'<U+001F>
      |                                                    ^
/home/user/.Xresources:205:33: warning: missing terminating '"' character [-Winvalid-pp-token]
  205 | URxvt.keysym.C-space: string:<U+001B><U+001F>P"<U+001F>
      |                                               ^
/home/user/.Xresources:208:37: warning: missing terminating ' character [-Winvalid-pp-token]
  208 | URxvt.keysym.S-C-1-space: string:<U+001B><U+001F>P'<U+001F>
      |                                                   ^
/home/user/.Xresources:211:32: warning: missing terminating '"' character [-Winvalid-pp-token]
  211 | URxvt.keysym.C-Menu: string:<U+001B><U+001F>R"<U+001F>
      |                                              ^
/home/user/.Xresources:216:36: warning: missing terminating ' character [-Winvalid-pp-token]
  216 | URxvt.keysym.S-C-1-Menu: string:<U+001B><U+001F>R'<U+001F>
      |                                                  ^
/home/user/.Xresources:226:36: warning: missing terminating ' character [-Winvalid-pp-token]
  226 | URxvt.keysym.S-C-1-Down: string:<U+001B><U+001F>T'<U+001F>
      |                                                  ^
/home/user/.Xresources:246:35: warning: missing terminating ' character [-Winvalid-pp-token]
  246 | URxvt.keysym.S-C-1-End: string:<U+001B><U+001F>X'<U+001F>
      |                                                 ^
32 warnings generated.

Can we solve this problem, somehow?

[CyberShadow]

Hi, can you try this patch?

diff --git a/term-keys-urxvt.el b/term-keys-urxvt.el
index 5a0ee68..d0f4d74 100644
--- a/term-keys-urxvt.el
+++ b/term-keys-urxvt.el
@@ -114,6 +114,19 @@ executable file and used for launching urxvt."
    " \\\n\t\"$@\"\n"))
 
 
+(defun term-keys/urxvt-escape-for-xresources (str)
+  "Escape special characters in STR for use in .Xresources.
+
+Escapes characters that would be interpreted by the C preprocessor
+\(run by xrdb) as string/character delimiters."
+  (apply #'concat
+         (mapcar (lambda (c)
+                   (pcase c
+                     (?\" "\\042")  ; double quote
+                     (?\' "\\047")  ; single quote
+                     (_   (string c))))
+                 str)))
+
 (defun term-keys/urxvt-xresources ()
   "Construct urxvt configuration in the form of .Xresources entries.
 
@@ -126,11 +139,13 @@ The returned string is suitable to be added as-is to an
   (apply #'concat
 	 (term-keys/iterate-keys
 	  (lambda (index keymap mods)
-	    (format "URxvt.keysym.%s: string:%s%s%s\n"
+	    (format "URxvt.keysym.%s: string:%s\n"
 		    (term-keys/urxvt-format-key keymap mods)
-		    term-keys/prefix
-		    (term-keys/encode-key index mods)
-		    term-keys/suffix)))))
+                    (term-keys/urxvt-escape-for-xresources
+                     (concat
+                      term-keys/prefix
+                      (term-keys/encode-key index mods)
+                      term-keys/suffix)))))))
 
 
 (defun term-keys/urxvt-run-emacs ()

BTW, personally I don't use the Xresources approach because it's global and affects all urxvt instances; term-keys/urxvt-args is more manageable (e.g. for a separate term-for-emacs script).

[rosso-]

I'll try it.
Thank You.
I'm running emacsd at system level and would like for the whole Xorg be ready to support such configuration.
Maybe I'll add some checks to emacs's init.el to load term-keys conditionally dependent of current environment (Xorg/plain terminal).
Static configuration is more robust, I think.

[CyberShadow]

I'm running emacsd at system level and would like for the whole Xorg be ready to support such configuration.

No problem.

Maybe I'll add some checks to emacs's init.el to load term-keys conditionally dependent of current environment (Xorg/plain terminal).

No need, that's not where the issue is.

The Xresources configures rxvt, not Emacs. Do you plan to use rxvt to run anything other than Emacs (e.g. a shell or other TUI apps)?

[rosso-]

The Xresources configures rxvt, not Emacs. Do you plan to use rxvt to run anything other than Emacs (e.g. a shell or other TUI apps)?

Yes I do %)
I use not so much terminal shortcuts: Ctrl+C, Ctrl+D, Ctrl+W, Ctrl+A, Ctrl+K, Ctrl+E, Ctrl+U, Alt+D, that's all I think.
Any problems may arise?

[CyberShadow]

Well, you may see some funny characters if you press a key that term-keys thinks can't be normally encoded in a way Emacs would have understood it. This might or might not be a problem for you.

[rosso-]

It works, I should make more tests.