Hi jethro,
Using the script you provided:

Code:

awk 'NR>1 {print > FILENAME"."(NR-1)}' RS="--dump[^\n]*" file

on Mac OS X I get:

Code:

awk: syntax error at source line 1
 context is
	NR>1 {print > >>>  FILENAME"." <<< 
awk: illegal statement at source line 1
awk: illegal statement at source line 1

The standards explicitly say that it is unspecified whether:

Code:

print > FILENAME"."(NR-1)

is interpreted as:

Code:

(print > FILENAME)"."(NR-1)

(as it is in awk on OS X) or as:

Code:

print > (FILENAME"."(NR-1))

(as it is on your system).
Changing your code to:

Code:

awk 'NR>1 {print > (FILENAME"."(NR-1))}' RS="--dump[^\n]*" file

with a file named file containing:

Code:

--dump-4564564.some.jibberish.whatever
From: user@domain.com
To: myfriend@email.com

Email Body

Best Regards,
Email Author

--dump-789789863.random.numbers.maybe
From: anotheruser@domain.com
To: someguy@planet.earth

Email Body

Your Friend,
another user

I get 6 files as shown here:

Code:

-rw-r--r--  1 dwc  staff     1 Apr 25 20:32 file.1
-rw-r--r--  1 dwc  staff     5 Apr 25 20:32 file.2
-rw-r--r--  1 dwc  staff   119 Apr 25 20:32 file.3
-rw-r--r--  1 dwc  staff     1 Apr 25 20:32 file.4
-rw-r--r--  1 dwc  staff     5 Apr 25 20:32 file.5
-rw-r--r--  1 dwc  staff   126 Apr 25 20:32 file.6

where file.1 and file.4 contain only a <newline> character; file.2 and file.5 contain "dump" and the line terminating <newline> character; and file.3 and file.6 contain the requested mail messages plus the tail end of the headers:
file.3:

Code:

4564564.some.jibberish.whatever
From: user@domain.com
To: myfriend@email.com

Email Body

Best Regards,
Email Author

file.6:

Code:

789789863.random.numbers.maybe
From: anotheruser@domain.com
To: someguy@planet.earth

Email Body

Your Friend,
another user

Note that there are two empty lines at the end of both of the above files. I believe that only one empty line was expected.

The number of file descriptors used by awk for open input and output streams is implementation defined. Some versions of awk used to limit you to 9 open files. Most systems today allow around 1024 or 2048 file descriptors per process and (unless you have privileges to up that limit before you invoke awk), awk won't be able to have more files open than the number of file descriptors available to it. You may have noticed that my script closed the previous output file before opening the next output file. This is usually a much better practice unless you know that your script will open less than ten files in its lifetime.

---------------

OOPS. I originally said that file.2 and file.5 contained "code". That has been corrected above. They contain "dump"; not "code".