joinlines: add thing

joinlines/main.go

···
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	if err := realMain(
+		os.Args,
+		os.Stdin,
+		os.Stdout,
+	); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func realMain(
+	args []string,
+	in io.Reader,
+	out io.Writer,
+) error {
+	fs := flag.NewFlagSet(args[0], flag.ExitOnError)
+	flagDelim := fs.String("d", ",", "delimiter")
+	fs.Parse(args[1:])
+
+	scanner := bufio.NewScanner(in)
+	first := true
+
+	for scanner.Scan() {
+		if first {
+			first = false
+		} else {
+			fmt.Fprint(out, *flagDelim)
+		}
+
+		line := scanner.Text()
+		fmt.Print(line)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+
+	fmt.Fprintln(out)
+
+	return nil
+}