Bash command to clear the VSCode integrated terminal scrollback on Windows 10?

[denishowe]

Issue Type: Bug

I'm happily running Git bash in VSCode on Windows with:

"terminal.integrated.shell.windows": "C:\\Program Files\\Git\\bin\\bash.exe",

The "Terminal: Clear" command (workbench.action.terminal.clear, which I have bound to Control-L) clears not only the screen but also the scrollback buffer, as expected, so trying to scroll up does nothing because there is nothing to show.

How can I reproduce this with a shell command?

The clear command does not clear the scrollback, neither does reset. These commands work by outputting escape sequences to the screen. Since the terminal thinks it is "TERM = xterm-256color", the relevant escape sequence should be the one output by the shell command printf "\e[3J" which works on all other xterm emulations (and is part of clear's output). In VSCode it does not clear the scrollback but, oddly, resurrects one screenful of previously cleared scrollback.

VS Code version: Code 1.53.2 (622cb03, 2021-02-11T11:48:04.245Z)
OS version: Windows_NT x64 10.0.19042

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (8 x 3392)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on protected_video_decode: unavailable_off rasterization: enabled skia_renderer: enabled_on video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.96GB (10.40GB free)
Process Argv	--crash-reporter-id 13260536-d995-489d-8f04-2bc386bb128a
Screen Reader	no
VM	0%

Extensions (4)

Extension	Author (truncated)	Version
vscode-eslint	dba	2.1.14
seito-openfile	Fr4	1.8.7
gc-excelviewer	Gra	3.0.41
org-mode	vsc	1.0.0

A/B Experiments

vsliv368:30146709
vsreu685:30147344
python383cf:30185419
pythonvspyt617cf:30253240
vspor879:30202332
vspor708:30202333
vspor363:30204092
vswsl492cf:30256860
vstry244cf:30256637
pythonvsdeb440:30248342
pythonvsded773:30248341
pythonvspyt600cf:30251589

[Tyriar]

Related to xtermjs/xterm.js#106

Not sure we can do anything about this as I believe we handle the sequence we're given correctly.

[Tyriar]

You can check what VS Code receives from the pty by logging escape sequences https://github.com/microsoft/vscode/wiki/Terminal-Issues#enabling-escape-sequence-logging

[denishowe]

Thanks Tyriar. I executed this command in bash:

sleep 2; printf "(\e[3J)"; sleep 99

I cleared the dev console during the sleep 2. During the sleep 99, the console showed:

xterm.js: parsing data ()�[0K

Something deleted my \e[3J.

workbench.action.terminal.clear clears scrollback but also shows nothing in dev console.

[Tyriar]

Looks like something is going wrong with the emulation here that causes your sequence to get stripped out? When you run printf it would go through git bash and then through conpty before reaching the process, and those layers are passed through again when coming the other direction. You could try:

• Updating Windows
• Updating git bash
• Trying in Windows Terminal (if it's fixed, we should get the fix in a newer release of Windows)

[TYTheBeast]

Although this is a really old issue, it's still relevant. Even today, no matter whether I'm running cmd, Powershell 7, Git Bash or any other profile, their respective clear command only clears one screenful of the terminal, without actually clearing the scrollback buffer.

[Tyriar]

@TYTheBeast that's tracked in xtermjs/xterm.js#1727

[danyg]

Workarround that worked for me in zsh in mac
add to your ~/.zshrc the following line

alias clear='printf "\e[3J"; clear'

I guess similar approaches can be done with other shells.
for windows shells you might be able to create a bat in the PATH that overrides cls? not sure.

HTH

[mike-clark-8192]

Under cmd.exe inside VSCode, none of the "clear" termcodes will clear the scrollback, even though at least a few of them probably should.

In fact, the plain old 'cls' command should clear the scrollback, as it does under the classic cmd window, and also the new Windows Terminal. But, it does not. Here is a .bat file that tests/exercises the various 'clear' terminal control codes. Running this inside VSCode will not result in a scrollback clear, whereas in Windows Terminal, it will.

@echo off
setlocal enableextensions

call :testit "[3J" "erase scrollback"         || exit /b
call :testit "[2J" "erase all"                || exit /b
call :testit "[1J" "erase above"              || exit /b
call :testit "[0J" "erase below"              || exit /b
call :testit "[J"  "erase below (alternate)"  || exit /b
call :testit "c"   "reset term"               || exit /b
echo Done.

goto :eof
:testit
REM this loop will probably reach the scrollback on most window sizes
for /l %%F in (30,1,37) do (
    for /l %%B in (40,1,47) do (
        call :echoe "\x1b[%%F;%%Bm%%F;%%B\x1b[0m"
    )
)
echo. & echo.
set /p "_=Press enter to test %1 (%~2): "
if "%_%"=="q" exit /b 1
call :echoe \x1b%1
echo Sending of %1 (%~2) is complete.
if "%~1"=="c" exit /b && REM "(exit because c is the last test)"
set /p "_=Press enter to move on to the next test."
exit /b 0
goto :eof

goto :eof
:echoe
setlocal
set "arg=%~1"
set "arg=%arg:\x=0x%"
forfiles /p "%~dp0." /m "%~nx0" /c "cmd /c <nul set /p _=%arg%"
goto :eof

[D3Pheonix]

for me, it works: