Question

For some reason I need to fetch emails from /var/mail/username file. It seems like an append only file.

My question is, is it safe to parse the content of the /var/email/username file depending on the first line From username@host Mon Jun 20 16:50:15 2011? What if the similar pattern found inside the email body?

Furthermore, is there any opensource ruby script available for reference?

Answer 1

Yes, that seems like more or less the right way to parse the mbox format – from a quick scan of the RFC specification:

The structure of the separator lines
vary across implementations, but
usually contain the exact character
sequence of "From", followed by a
single Space character (0x20), an
email address of some kind, another
Space character, a timestamp sequence
of some kind, and an end-of- line
marker.

And…

Many implementations are also known
to escape message body lines that
begin with the character sequence of
"From ", so as to prevent confusion
with overly-liberal parsers that do
not search for full separator
lines. In the common case, a leading
Greater-Than symbol (0x3E) is used
for this purpose (with "From "
becoming ">From "). However, other
implementations are known not to
escape such lines unless they are
immediately preceded by a blank line
or if they also appear to contain
an email address and a timestamp.
Other implementations are also
known to perform secondary escapes
against these lines if they are
already escaped or quoted, while
others ignore these mechanisms
altogether.

Update:
There’s also this: https://github.com/meh/ruby-mbox