Linux – Compress Command Output by Piping to bzip2

export BZIP=--fast
tar cjf foo.tar.bz2 foo

Or pipe the output of tar to bzip2.

Though you should note from the bzip2 man page:

    -1 (or --fast) to -9 (or --best)
              Set  the  block size to 100 k, 200 k ..  900 k when compressing.
              Has no effect when decompressing.  See MEMORY MANAGEMENT  below.
              The --fast and --best aliases are primarily for GNU gzip compat-
              ibility.  In particular, --fast  doesn't  make  things  signifi-
              cantly faster.  And --best merely selects the default behaviour.

This is the cleanest way to do what you want:

mutt admin@example.org -a <(mysqldump mysqldumpoptions)

The <() operator is what you were asking for; it creates a FIFO (or /dev/fd) and forks a process and connects stdout to the FIFO. >() does the same, except connects stdin to the FIFO instead. In other words, it does all the mknod stuff for you behind the scenes; or on a modern OS, does it in an even better way.

Except, of course, that doesn't work with mutt, it says:

/dev/fd/63: unable to attach file.

I suspect the problem is that mutt is trying to seek in the file, which you can't do on a pipe of any sort. The seeking is probably something like scanning the file to figure out what MIME type it is and what encodings might work (ie, whether the file is 7bit or 8bit), and then seeking to the beginning of the file to actually encode it into the message.

If what you want to send is plain text, you could always do something like this to make it the main contents of the email instead (not ideal, but it actually works):

mysqldump mysqldumpoptions | mutt -s "Here's that mysqldump" admin@example.org