Fail with a clear error when device monitor stdin is not a TTY - #5503
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ivankravets merged 2 commits intoAug 25, 2026
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`pio device monitor` crashed with a raw termios traceback
("Inappropriate ioctl for device") whenever stdin was piped or
redirected instead of a real terminal, e.g. `echo "" | pio device
monitor`. This happened because pyserial's Miniterm.Console tries to
call termios.tcgetattr() on stdin during Terminal construction, which
only works on a real TTY.
Detect non-TTY stdin before constructing the Terminal and raise a
clear UserSideException instead, pointing users toward talking to the
serial port directly (e.g. with pyserial) if they're trying to
automate device I/O from a script.
Fixes platformio#5113
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Pull request overview
This PR improves the UX and reliability of pio device monitor by preventing a low-level termios crash when stdin is not an interactive TTY (e.g., when piped or redirected), and instead raising a clear, actionable UserSideException.
Changes:
- Add an early stdin TTY check in
new_terminal()to fail fast with a user-friendly error. - Add a regression test that mocks non-TTY stdin and asserts the expected
UserSideException.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| platformio/device/monitor/terminal.py | Adds early stdin TTY validation and raises a clear UserSideException before constructing the miniterm console. |
| tests/commands/test_device_monitor.py | Adds a regression test covering the non-TTY stdin behavior and expected error message. |
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Summary
pio device monitorcrashes with a raw termios traceback (Inappropriate ioctl for device) whenever stdin is piped or redirected instead of a real terminal, e.g.echo "" | pio device monitor. This happens because pyserial'sMiniterm.Consolecallstermios.tcgetattr()on stdin duringTerminalconstruction, which only works when stdin is an actual TTY.This PR detects non-TTY stdin before constructing the
Terminaland raises a clearUserSideExceptioninstead, pointing users toward talking to the serial port directly (e.g. with pyserial) if they're trying to automate device I/O from a script, which was the reporter's use case.Fixes #5113
Changes
platformio/device/monitor/terminal.py: checksys.stdin.isatty()at the top ofnew_terminal()before any serial/terminal setup happenstests/commands/test_device_monitor.py: regression test that mocks a non-TTY stdin and asserts the clear error is raisedTest plan
pytest tests/commands/test_device_monitor.py -v— all 4 tests pass (3 existing + 1 new)make lint(pylint) — 10.00/10 on both changed filesblack --check/isort --check-only— clean, no changes neededcodespell— clean