Initial commit

baudshell.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""pty_baud.py – run a shell behind two baud-rate simulators."""
+import os, pty, sys, tty, termios, select, subprocess
+
+BAUD  = sys.argv[1] if len(sys.argv) > 1 else "baud"
+SHELL = ["bash", "--norc"]
+
+master, slave = pty.openpty()
+shell = subprocess.Popen(SHELL, stdin=slave, stdout=slave, stderr=slave,
+                         preexec_fn=os.setsid, close_fds=True)
+os.close(slave)
+
+baud_out = subprocess.Popen([BAUD], stdin=subprocess.PIPE,
+                            stdout=subprocess.PIPE)
+baud_in  = subprocess.Popen([BAUD], stdin=subprocess.PIPE,
+                            stdout=subprocess.PIPE)
+
+# ── flatten every endpoint to an int fd ──────────────────────────
+fd_term          = sys.stdin.fileno()
+fd_baud_in_stdin = baud_in.stdin.fileno()
+fd_baud_in_out   = baud_in.stdout.fileno()
+fd_baud_out_in   = baud_out.stdin.fileno()
+fd_baud_out_out  = baud_out.stdout.fileno()
+# master is already an int from openpty()
+
+old = termios.tcgetattr(fd_term)
+tty.setraw(fd_term)
+
+def pump(r, w):
+    try:
+        d = os.read(r, 4096)          # r is already an int
+    except OSError:
+        return False
+    if not d:
+        return False
+    try:
+        os.write(w, d)                # w is already an int
+    except OSError:
+        return False
+    return True
+
+try:
+    while True:
+        r, _, _ = select.select(
+            [fd_term, master, fd_baud_in_out, fd_baud_out_out],
+            [], [], 0.01)
+
+        if fd_term          in r: pump(fd_term,          fd_baud_in_stdin)
+        if master           in r: pump(master,           fd_baud_out_in)
+        if fd_baud_in_out   in r: pump(fd_baud_in_out,   master)
+        if fd_baud_out_out  in r: pump(fd_baud_out_out,  fd_term)
+except KeyboardInterrupt:
+    pass
+finally:
+    termios.tcsetattr(fd_term, termios.TCSADRAIN, old)
+    for p in (shell, baud_in, baud_out):
+        try: p.terminate()
+        except OSError: pass
+