roundtrip_qr.py: detect the active tty

UC20 seems to deviate from the norm of tty1 being the active tty after install. Update the script to detect which is active. 

1 files changed, 16 insertions, 3 deletions

diff --git a/bin/roundtrip_qr.py b/bin/roundtrip_qr.py
index e2eb5b5..c3494e2 100755
--- a/bin/roundtrip_qr.py
+++ b/bin/roundtrip_qr.py
@@ -61,8 +61,14 @@ def generate_qr_code(data):
 return pyqrcode.create(data)
 
 
-def display_code(qr):
- with open('/dev/tty1', 'wb+', buffering=0) as term:
+def get_active_tty():
+ with open('/sys/class/tty/tty0/active', 'r') as active_f:
+ return active_f.read().strip()
+
+
+def display_code(qr, tty):
+ device = '/dev/{}'.format(tty)
+ with open(device, 'wb+', buffering=0) as term:
 # clear the tty so the qr is always printed at the top of the sceen
 term.write(str.encode('\033c'))
 # print the qr code
@@ -98,8 +104,15 @@ def main():
 print('Generating QR code...', flush=True)
 qr = generate_qr_code(test_str)
 
+ tty = 'tty1'
+ try:
+ tty = get_active_tty()
+ print('Identified {} as the active vt'.format(tty))
+ except IOError:
+ print('Failed to read active tty, using default {}'.format(tty))
+
 print('Displaying on screen', flush=True)
- display_code(qr)
+ display_code(qr, tty)
 
 print('Capture image of screen', flush=True)
 if name == 'vchiq':