Decode base64 from “content-disposition: attachment” body part - email

Question

I am trying to extract message body using procmail be it in the message or in an attachment, but I got first two characters from below:
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* ^()[a-z]+[0-9]+[^\+]
{ msgID = "$MATCH" }
:0B
* ^Content-Disposition: *attachment.*(($)[a-z0-9].*)*($)($)\/[a-z]+[0-9]+
| base64 --decode
{ msgID = "$MATCH" }
The decoding of base64 is not working, it's either not matching as whole condition, or assigning LASTFOLDER=base64 --decode"
See also my earlier question

Answer 1

You can't have two actions on a single recipe. Where you have
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* ^stuff\/more stuff
{ msgid="$MATCH" }
| base64 --decode
the second line is a syntax error. I'm guessing you mean something like
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* ^stuff\/more stuff
{
msgid="$MATCH"
:0
| base64 --decode
}
See? If you need more than one action, add a pair of braces (don't forget the closing braces at the end!) around another group of recipes as the action section. Maybe see also http://www.iki.fi/era/procmail/quickref.html
But in your case, you apparently want to extract the token base64 decoded, so the code you are looking for would be
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* ^Content-Disposition: *attachment.*(($)[a-z0-9].*)*($)($)\/[a-z]+[0-9]+
{ msgID=`echo "$MATCH" | base64 --decode` }
Notice also that you cannot have a space around the equals sign. And the regex is incorrect for arbitrary base64; plus and slash are also among the allowed characters, and equals at the end. Change the part after \/ to [a-z0-9/+]+=*