Try adding the full path the curl executable. I highlighted it in red. Also use the full path for the variable also in red.
EDIT:Code:#!/bin/bash BACKUPDIR=/usr/local/ CONTENT1=/usr/local/etc/squid BACKUPFILE=squid.backup.`date +%F` tar -czvf $BACKUPDIR/$BACKUPFILE $CONTENT1 /usr/bin/curl -v -T $BACKUPDIR/squid.back* #END
Also curl is used for transferring URLS, I don't see any FTP parts happening in your script. You can probably use cp command instead of curl.