main.go

package main

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"os/exec"
	"runtime"
)

func command(path string, args ...string) *exec.Cmd {
	return exec.Command(path, args...)
}

func main() {
	l := log.New(os.Stderr, "", log.Ldate|log.Lmicroseconds)
	l.Printf("start w/%s", runtime.Version())

	input := command("echo", "ababa")
	input.Stderr = os.Stderr
	filterOut := new(bytes.Buffer)
	filter := command("sed", "s/a/A/g")
	filter.Stdout = filterOut
	var err error
	filter.Stdin, err = input.StdoutPipe()
	if err != nil {
		fmt.Printf("! cannot open stdout pipe: %+v\n", err)
		os.Exit(1)
	}
	l.Printf("%s start", input.Path)
	if err := input.Start(); err != nil {
		fmt.Printf("! cannot start %s: %+v\n", input.Path, err)
		os.Exit(1)
	}
	l.Printf("%s start", filter.Path)
	if err := filter.Start(); err != nil {
		fmt.Printf("! cannot start %s: %+v\n", filter.Path, err)
		os.Exit(1)
	}
	l.Printf("waiting for %s", input.Path)
	if err := input.Wait(); err != nil {
		fmt.Printf("! fail %s: %+v\n", input.Path, err)
		os.Exit(1)
	}
	l.Printf("waiting for %s", filter.Path)
	if err := filter.Wait(); err != nil {
		fmt.Printf("! fail %s: %+v\n", filter.Path, err)
		os.Exit(1)
	}
	fmt.Printf("filter output: %s\n", filterOut.String())
}

result.godevplay.txt

# from https://go.dev/play/p/mf0DsQHVAJN

2009/11/10 23:00:00.000000 start w/Go go1.17.8
2009/11/10 23:00:00.000000 /bin/echo start
2009/11/10 23:00:00.000000 /bin/sed start
2009/11/10 23:00:00.000000 waiting for /bin/echo
2009/11/10 23:00:00.000000 waiting for /bin/sed
filter output: AbAbA


Program exited.

result.macos.txt

[2022-03-06 22:31:57] ✘╹◡╹✘ < go build -o a ./tmp
[2022-03-06 22:32:21] ✘╹◡╹✘ < ./a
2022/03/06 22:32:33.775941 start w/go1.17.7
2022/03/06 22:32:33.776988 /usr/local/opt/coreutils/libexec/gnubin/echo start
2022/03/06 22:32:44.449082 /usr/bin/sed start
2022/03/06 22:32:55.098631 waiting for /usr/local/opt/coreutils/libexec/gnubin/echo
2022/03/06 22:32:55.098678 waiting for /usr/bin/sed
filter output: AbAbA
[2022-03-06 22:34:19] ✘╹◡╹✘ < uname -s -r -v -m -p
Darwin 19.6.0 Darwin Kernel Version 19.6.0: Tue Oct 12 18:34:05 PDT 2021; root:xnu-6153.141.43~1/RELEASE_X86_64 x86_64 i386