Allow sending arbitrary signals to the current foreground process in a window using either a mapping in kitty.conf or via remote control

Fixes #2778

docs/changelog.rst

@@ -15,6 +15,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Tall and Fat layouts: Add mappable actions to increase or decrease the number
   of full size windows (:iss:`2688`)
 
+- Allow sending arbitrary signals to the current foreground process in a window
+  using either a mapping in kitty.conf or via remote control (:iss:`2778`)
+
 - Allow sending the back and forward mouse buttons to terminal applications
   (:pull:`2742`)
 

kitty/config.py

@@ -140,6 +140,20 @@ def float_parse(func: str, rest: str) -> FuncArgsType:
     return func, (float(rest),)
 
 
+@func_with_args('signal_child')
+def signal_child_parse(func: str, rest: str) -> FuncArgsType:
+    import signal
+    signals = []
+    for q in rest.split():
+        try:
+            signum = getattr(signal, q.upper())
+        except AttributeError:
+            log_error(f'Unknown signal: {rest} ignoring')
+        else:
+            signals.append(signum)
+    return func, tuple(signals)
+
+
 @func_with_args('change_font_size')
 def parse_change_font_size(func: str, rest: str) -> Tuple[str, Tuple[bool, Optional[str], float]]:
     vals = rest.strip().split(maxsplit=1)

kitty/rc/signal_child.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2020, Kovid Goyal <kovid at kovidgoyal.net>
+
+from typing import TYPE_CHECKING, Optional
+
+from .base import (
+    MATCH_WINDOW_OPTION, ArgsType, Boss, MatchError, PayloadGetType,
+    PayloadType, RCOptions, RemoteCommand, ResponseType, Window
+)
+
+if TYPE_CHECKING:
+    from kitty.cli_stub import SignalChildRCOptions as CLIOptions
+
+
+class SignalChild(RemoteCommand):
+
+    '''
+    signals: The signals, a list of names, such as SIGTERM, SIGKILL, SIGUSR1, etc.
+    match: Which windows to change the title in
+    '''
+
+    short_desc = 'Send a signal to the foreground process in the specified window'
+    desc = (
+        'Send one or more signals to the foreground process in the specified window(s).'
+        ' If you use the :option:`kitty @ signal-child --match` option'
+        ' the title will be set for all matched windows. By default, only the active'
+        ' window is affected. If you do not specify any signals, :code:`SIGINT` is sent by default.'
+        ' You can also map this to a keystroke in kitty.conf, for example::\n\n'
+        '    map F1 signal_child SIGTERM'
+    )
+    options_spec = '''\
+    ''' + '\n\n' + MATCH_WINDOW_OPTION
+    argspec = '[SIGNAL_NAME ...]'
+
+    def message_to_kitty(self, global_opts: RCOptions, opts: 'CLIOptions', args: ArgsType) -> PayloadType:
+        return {'match': opts.match, 'signals': [x.upper() for x in args] or ['SIGINT']}
+
+    def response_from_kitty(self, boss: Boss, window: Optional[Window], payload_get: PayloadGetType) -> ResponseType:
+        import signal
+        windows = [window or boss.active_window]
+        match = payload_get('match')
+        if match:
+            windows = list(boss.match_windows(match))
+            if not windows:
+                raise MatchError(match)
+        signals = tuple(getattr(signal, x) for x in payload_get('signals'))
+        for window in windows:
+            if window:
+                window.signal_child(*signals)
+
+
+signal_child = SignalChild()

kitty/window.py

@@ -820,4 +820,10 @@ class Window:
 
     def scroll_to_mark(self, prev: bool = True, mark: int = 0) -> None:
         self.screen.scroll_to_next_mark(mark, prev)
+
+    def signal_child(self, *signals: int) -> None:
+        pid = self.child.pid_for_cwd
+        if pid is not None:
+            for sig in signals:
+                os.kill(pid, sig)
     # }}}