Extract mail header and decode MIME encoded-word

Question

As part of a script, I want to take a file containing an email and extract a header, e.g., the subject header. The following almost works:

formail -c -x subject < FILE

But it does not decode headers encoded using the MIME encoded-word syntax (aka RFC2047), e.g., =?UTF-8?B?w6lsw6ltZW50?=.

What's a nice way to extract an email header while taking care of decoding MIME encoded-word parts?

Related question: https://stackoverflow.com/questions/39457380/retrieve-email-subject-from-file-via-bash

Answer 1

pipe it to:

python)

formail -c -x Subject < FILE | \
python -c "from email.header import decode_header;
import sys;
text, encoding = decode_header(sys.stdin.read())[0];
print text.decode(encoding)"

php)

formail -c -x Subject < FILE | \
  php -r 'echo iconv_mime_decode(stream_get_contents(STDIN),1,"utf-8");'

or if you're sure that the header will be =?UTF-8?B?… then you can easily do:

formail -c -x Subject < FILE | \
  awk -F '[?]' '{print $4}' | \
  openssl enc -base64 -d -A

python should be probably most universal, since it is in probably all systems by default and even the email module is present.