x/term: Why IsTerminal reports true on redirected stdout? [unrelated]

[gabyx]

What version of Go are you using (go version)?

1.15.2

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/gabyx/Library/Caches/go-build"
GOENV="/Users/gabyx/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/gabyx/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/gabyx/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.15.2/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.15.2/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/gabyx/Desktop/githooks/githooks/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/jf/0dqq5t6x0rxd9kkp8vmc18gc0000gn/T/go-build702825481=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

package main

import (
	"fmt"
	"golang.org/x/term"
	"os"
)

func main() {
    if term.IsTerminal(int(os.Stdout.Fd())) {
        fmt.Println("Is Terminal")
    }
}

and run it with ./run 1> Log.txt.

What did you expect to see?

No output in Log.txt because stdout is redirected?

What did you see instead?

Is Terminal in Log.txt

[ianlancetaylor]

Your program doesn't compile:

foo.go:10:33: cannot use os.Stdout.Fd() (type uintptr) as type int in argument to term.IsTerminal

When I fix that, the program behaves as I expect:

> ./foo
Is Terminal
> ./foo > /tmp/x.txt
> cat /tmp/x.txt
>

Show us a way to reproduce the problem.

[gabyx]

Updated

[gabyx]

Really. I am on Darwin macOs in a Zsh shell. There it happens.

[gabyx]

I will provide more infos!

[davecheney]

@gabyx I am using darwin with zsh, I cannot reproduce your findings

(~/src) % go build term.go && ./term | tee log.out
(~/src) % cat log.out
(~/src) % go build term.go && ./term > log.out
(~/src) % cat log.out
(~/src) %

[gabyx]

Thx for that report. I will investigate later in 2 days Von meinem iPhone gesendet

…

Am 16.10.2020 um 08:10 schrieb Dave Cheney ***@***.***>: @gabyx I am using darwin with zsh, I cannot reproduce your findings (~/src) % go build term.go && ./term | tee log.out (~/src) % cat log.out (~/src) % go build term.go && ./term > log.out (~/src) % cat log.out (~/src) % — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

[gabyx]

Sorry for your precious time. I mistakenly used the compiled code under a hook invoked by git commit which is where I got confused -> git attaches its stderr to both stdout/stderr of the hook executable... hm...

This works fine.