How do I send a file as an email attachment using Linux command line?

I've created a script that runs every night on my Linux server that uses mysqldump to back up each of my MySQL databases to .sql files and packages them together as a compressed .tar file. The next step I want to accomplish is to send that tar file through email to a remote email server for safekeeping. I've been able to send the raw script in the body an email by piping the backup text file to mailx like so:

$ cat mysqldbbackup.sql | mailx [email protected]

cat echoes the backup file's text which is piped into the mailx program with the recipient's email address passed as an argument.

While this accomplishes what I need, I think it could be one step better, Is there any way, using shell scripts or otherwise, to send the compressed .tar file to an outgoing email message as an attachment? This would beat having to deal with very long email messages which contain header data and often have word-wrapping issues etc.

None of the mutt ones worked for me. It was thinking the email address was part of the attachemnt. Had to do:

echo "This is the message body" | mutt -a "/path/to/file.to.attach" -s "subject of message" -- [email protected]

Or, failing mutt:

gzip -c mysqldbbackup.sql | uuencode mysqldbbackup.sql.gz  | mail -s "MySQL DB" [email protected]

Depending on your version of linux it may be called mail. To quote @David above:

mail -s "Backup" -a mysqldbbackup.sql [email protected] < message.txt

or also:

cat message.txt | mail -s "Backup" -a mysqldbbackup.sql [email protected] 

From looking at man mailx, the mailx program does not have an option for attaching a file. You could use another program such as mutt.

echo "This is the message body" | mutt -a file.to.attach -s "subject of message" [email protected]

Command line options for mutt can be shown with mutt -h.