mkfile.go

// Generate a test input for rmchar.go.
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	w := bufio.NewWriter(os.Stdout)
	fmt.Fprintln(w, "hello there")
	for r := '\200'; r <= '\377'; r++ {
		fmt.Fprint(w, string(r))
	}
	fmt.Fprintln(w, "okay, all done")
	w.Flush()
}

rmchar.go

// Remove chars \200 through \377 from input.
package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

func main() {
	var (
		in = bufio.NewReader(os.Stdin)
		out = bufio.NewWriter(os.Stdout)
		err error
	)
	for {
		var r rune
		r, _, err = in.ReadRune()
		if err != nil {
			break
		}
		if r >= '\200' && r <= '\377' {
			continue
		}
		_, err = out.WriteRune(r)
		if err != nil {
			break
		}	
	}
	if err != io.EOF {
		fmt.Fprintf(os.Stderr, "error: %v\n", err)
	}
	out.Flush()
}