mailparse/cmd/mailparse/cli.go

package main

/* Finds (1st occurrence of) a specific header */

import (
	"bufio"
	"encoding/json"
	"flag"
	"fmt"
	"net/mail"
	"net/textproto"
	"os"
)

func main() {
	reader := bufio.NewReader(os.Stdin)
	m, err := mail.ReadMessage(reader)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	flag.Parse()
	headers := textproto.MIMEHeader(m.Header)
	if len(flag.Args()) > 0 {
		results := make([]string, 0)
		for _, needle := range flag.Args() {
			values := headers[textproto.CanonicalMIMEHeaderKey(needle)]
			if len(values) == 0 {
				fmt.Fprintf(os.Stderr, "No values for field `%s`\n", needle)
			} else {
				results = append(results, string(values[0]))
			}
		}
		for _, res := range results {
			fmt.Println(res)
		}
		os.Exit(0)
	} else {
		enc, err := json.Marshal(headers)
		if err != nil {
			fmt.Fprintln(os.Stderr, "Error serializing mail headers")
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}
		fmt.Println(string(enc))
		os.Exit(0)
	}
}