Re: "cat" breaks ANSI codes on Windows Terminal when piping stdout to python or golang

[Takashi Yano <takashi.yano@nifty.ne.jp>]

On Tue, 14 Jun 2022 08:01:45 +0000
5990 via Cygwin wrote:
> ## Bug:
> Piping the standard output of cat into the standard input of golang or python, makes the Windows Terminal render ANSI codes as arrows.
> 
> For example:
> `\033[36m` turns into `←[36m` (or in base64'd UNICODE: `4oaQWzM2bQ==`)
> 
> ## Environment:
> - cat v8.26
> - Windows Terminal v1.12.10982.0
> - golang version go1.17.2 windows/amd64
> - python v3.7.7
> 
> colors.go
> ```
> package main
> 
> import "fmt"
> 
> const colorReset = "\033[0m"
> const colorCyan = "\033[36m"
> 
> func main(){
>   fmt.Print(string(colorCyan) + "golang-test" + string(colorReset) + "\n")
> }
> ```
> 
> 
> color.py
> ```
> from lolpython import lol_py
> 
> lol_py("python-test")
> ```
> 
> 
> domains.txt is an empty file (from my testing, the contents of domains.txt do not affect this bug)
> 
> ## What works:
> The following commands will successfuly output in cyan color
> `go run color.go`
> `go build color.go && color.exe`
> `go build color.go && cat domains.txt | color.exe`
> `go build color.go && echo a | color.exe`
> `go build color.go && type domains.txt | color.exe`
> `py -3.7 color.py`
> 
> ## What triggers the bug:
> `cat domains.txt | go run color.go`
> OUTPUT: `←[36mgolang-test←[0m`
> 
> `cat domains.txt | py -3.7 color.py`
> OUTPUT: `←[38;2;128;237;18mp←[0m←[38;2;139;231;12my←[0m←[38;2;150;225;8mt←[0m←[38;2;161;217;5mh←[0m←[38;2;172;209;2mo←[0m←[38;2;182;200;1mn←[0m←[38;2;192;190;1m-←[0m←[38;2;201;180;1mt←[0m←[38;2;210;170;3me←[0m←[38;2;218;159;5ms←[0m←[38;2;226;148;9mt←[0m`
> 
> Strangely enough, golang compiled executables work perfectly, but piping `cat domains.txt | go run color.go` does not work.
> The workaround I had to go with is to use Windows's built-in `type` command instead of `cat`. This was a tricky bug to track-down so I hope this report helps hahah

I cannot reproduce your problem.

My environment is:
cygwin 3.3.5
cat 8.32
Windows Terminal 1.13.11431.0
go version go1.18.3 windows/amd64

What shell did you use? cygwin bash? cmd.exe? powershell?

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>