add detect-size - detect and set real geometry of a terminal

CMakeLists.txt

@@ -163,6 +163,7 @@ set(scripts
     check-dnsbl.py
     chromium-extensions.py
     cpufreq.py
+    detect-size.py
     devof.sh
     disas.sh
     firefox-addons.py

README.md

@@ -31,6 +31,8 @@ This repository contains a collection of command line utilities.
     -- decompressing cat (autodetects gzip/zstd/bz2/...)
 - [dcheck](#dcheck)
     -- run a program under DBX's memory check mode
+- detect-size
+    -- detect and set real height/width of a terminal
 - devof
     -- list network device names given an address (prefix)
 - disas

detect-size.py

+#!/usr/bin/env python3
+
+# detect-size - detect and set real height/width of a terminal
+#
+# replacement for xterm's resize command for systems that
+# don't package it separately (e.g. in xterm-resize as Fedora does)
+#
+# useful for terminals that are attached to a serial line,
+# including emulated ones (e.g. on a VM)
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+# SPDX-FileCopyrightText: © 2021 Georg Sauthoff <mail@gms.tf>
+
+import fcntl
+import os
+import struct
+import sys
+import termios
+import tty
+
+def main():
+    # source: https://sources.debian.org/src/xterm/366-1/resize.c/?hl=137#L139
+    print('\x1b' '7' '\x1b' '[r' '\x1b' '[9999;9999H' '\x1b' '[6n',
+            flush=True, end='')
+    
+    # cf. https://stackoverflow.com/q/40931467/427158
+
+    bak = termios.tcgetattr(sys.stdin.fileno())
+    tty.setcbreak(sys.stdin.fileno())
+    r = b''.join(iter(lambda : os.read(sys.stdin.fileno(), 1), b'R'))
+    termios.tcsetattr(sys.stdin.fileno(), termios.TCSADRAIN, bak)
+
+    i = r.rindex(b'[')
+    j = r.index(b';')
+
+    h = int(r[i+1:j])
+    w = int(r[j+1:])
+
+    x = struct.pack('HHHH', h, w, 0, 0)
+
+    print(f'\rheight: {h}, width: {w}')
+
+    fcntl.ioctl(sys.stdout, termios.TIOCSWINSZ, x)
+
+    # alternatively: ioctl() on /dev/tty
+
+if __name__ == '__main__':
+    sys.exit(main())
+