Bash – Trying to do grep and sed from a file and push the output into a variable

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

You need curly braces around the whole command inside the command substitution but before the redirection:

result=$( { time wget -q --output-document=/tmp/wget.$$.html http://domain.tomonitor.com; } 2>&1; );

That captures the output of time. If you want to capture the error output of wget (you're already saving its regular output to a file), you'll need to do something a little different and it depends on what exactly you want to do. It may involve extra file descriptors or simply using the redirection I showed in my answer to your other question (instead of using --output-document).