Run the child process

kitty/boss.py

@@ -2,15 +2,11 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
-import os
-import fcntl
-import termios
-import struct
-
 from PyQt5.QtCore import QObject
 
 from .screen import Screen
 from .term import TerminalWidget
+from .utils import resize_pty, hangup
 
 
 class Boss(QObject):
@@ -20,7 +16,7 @@ class Boss(QObject):
         self.screen = Screen(opts, parent=self)
         self.term = TerminalWidget(opts, self.screen.linebuf, parent)
         self.term.relayout_lines.connect(self.relayout_lines)
-        self.master_fd, self.slave_fd = os.openpty()
+        resize_pty(self.screen.columns, self.screen.lines)
 
     def apply_opts(self, opts):
         self.screen.apply_opts(opts)
@@ -28,9 +24,9 @@ class Boss(QObject):
 
     def relayout_lines(self, previous, cells_per_line, previousl, lines_per_screen):
         self.screen.resize(lines_per_screen, cells_per_line)
-        fcntl.ioctl(self.master_fd, termios.TIOCSWINSZ, struct.pack('4H', cells_per_line, lines_per_screen, 0, 0))
+        resize_pty(cells_per_line, lines_per_screen)
 
     def shutdown(self):
-        os.close(self.slave_fd), os.close(self.master_fd)
         del self.master_fd
         del self.slave_fd
+        hangup()

kitty/main.py

@@ -16,6 +16,7 @@ from PyQt5.QtWidgets import QApplication, QMainWindow, QMessageBox
 from .config import load_config, validate_font
 from .constants import appname, str_version, config_dir
 from .boss import Boss
+from .utils import fork_child
 
 
 class MainWindow(QMainWindow):
@@ -70,7 +71,7 @@ def option_parser():
     a('--class', default=appname, dest='cls', help=_('Set the class part of the WM_CLASS property'))
     a('--config', default=os.path.join(config_dir, 'kitty.conf'), help=_('Specify a path to the config file to use'))
     a('--cmd', '-c', default=None, help=_('Run python code in the kitty context'))
-    a('--exec', '-e', default=pwd.getpwuid(os.geteuid()).pw_shell or '/bin/sh', help=_('Run the specified command instead of the shell'))
+    a('--exec', '-e', dest='child', default=pwd.getpwuid(os.geteuid()).pw_shell or '/bin/sh', help=_('Run the specified command instead of the shell'))
     a('-d', '--directory', default='.', help=_('Change to the specified directory when launching'))
     a('--version', action='version', version='{} {} by Kovid Goyal'.format(appname, '.'.join(str_version)))
     return parser
@@ -81,8 +82,10 @@ def main():
     if args.cmd:
         exec(args.cmd)
         return
+    # Ensure the child process gets no environment from Qt
     opts = load_config(args.config)
-    os.chdir(args.directory)
+    fork_child(args.child, args.directory, opts)
+
     QApplication.setAttribute(Qt.AA_DisableHighDpiScaling, True)
     app = QApplication([appname])
     app.setOrganizationName(args.cls)

kitty/utils.py

@@ -2,6 +2,12 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
+import os
+import termios
+import struct
+import shlex
+import fcntl
+import signal
 from functools import lru_cache
 
 from PyQt5.QtGui import QFontMetrics
@@ -24,3 +30,48 @@ def set_current_font_metrics(fm: QFontMetrics, cw: int) -> None:
     global current_font_metrics, cell_width
     current_font_metrics, cell_width = fm, cw
     wcwidth.cache_clear()
+
+
+def create_pty():
+    if not hasattr(create_pty, 'master'):
+        create_pty.master, create_pty.slave = os.openpty()
+        fcntl.fcntl(create_pty.slave, fcntl.F_SETFD, fcntl.fcntl(create_pty.slave, fcntl.F_GETFD) & ~fcntl.FD_CLOEXEC)
+    return create_pty.master, create_pty.slave
+
+
+def fork_child(cmd, cwd, opts):
+    argv = shlex.split(cmd)
+    master, slave = create_pty()
+    pid = os.fork()
+    if pid == 0:
+        try:
+            os.chdir(cwd)
+        except EnvironmentError:
+            os.chdir('/')
+        os.setsid()
+        for i in range(3):
+            os.dup2(slave, i)
+        os.close(slave), os.close(master)
+        # Establish the controlling terminal (see man 7 credentials)
+        os.close(os.open(os.ttyname(1), os.O_RDWR))
+        os.environ['TERM'] = opts.term
+        os.environ['COLORTERM'] = 'truecolor'
+        os.execvp(argv[0], argv)
+    else:
+        os.close(slave)
+        fork_child.pid = pid
+        return pid
+
+
+def resize_pty(w, h):
+    master = create_pty()[0]
+    fcntl.ioctl(master, termios.TIOCSWINSZ, struct.pack('4H', w, h, 0, 0))
+
+
+def hangup():
+    if hasattr(fork_child, 'pid'):
+        pid = fork_child.pid
+        del fork_child.pid
+        pgrp = os.getpgid(pid)
+        os.killpg(pgrp, signal.SIGHUP)
+        os.close(create_pty()[0])