Compressing single file instead of whole directory
#!/bin/sh

# Where to backup to.
mkdir -p /home/knoppix/backups --verbose
dest="/home/knoppix/backups"

# What to backup.
cat /etc/passwd >> /home/knoppix/backups/dbusers.txt
backupdb="/home/knoppix/backups/dbusers.txt"

# Create archive filename.
archive_file="DB$(date +%d%b%Y_%H%M).tgz"

# Print start status message.
echo "Backing up $backupdb to $dest/$archive_file"
date
echo

# Backup the files using tar.
tar czf $dest/$archive_file $backupdb

#!/bin/sh

# Where to backup to.
mkdir -p /home/knoppix/backups --verbose
dest="/home/knoppix/backups"

# What to backup.
cat /etc/passwd >> /home/knoppix/backups/dbusers.txt
backupdir="/home/knoppix/backups"
backupfile="dbusers.txt"

# Create archive filename.
archive_file="DB$(date +%d%b%Y_%H%M).tgz"

# Print start status message.
echo "Backing up $backupdb to $dest/$archive_file"
date
echo

# Backup the files using tar.
tar czf $dest/$archive_file -C $backupdir $backupfile

#!/bin/sh

# Where to backup to.
mkdir -p /home/knoppix/backups --verbose
dest="/home/knoppix/backups"

# What to backup.
cat /etc/passwd >> /home/knoppix/backups/dbusers.txt
backupdir="/home/knoppix/backups"
backupfile="dbusers.txt"

# Create archive filename.
archive_base_name="DB$(date +%d%b%Y_%H%M)"
archive_file="$archive_base_name.tgz"

# Print start status message.
echo "Backing up $backupdb to $dest/$archive_file"
date
echo

# Backup the files using tar.
tar --transform="s#^$base#$archive_base_name#" czPf $dest/$archive_file $backupdb

DB11Nov2011_0555/dbusers.txt

tar --transform="s#dbusers#original#" xzf example.tgz # creates original.txt
tar --transform="s#^#output/#" xzf example.tgz        # creates output/dbusers.txt

$ set -x
$ archive_file="DB$(date +%d%b%Y_%H%M).tgz"
++ date +%d%b%Y_%H%M
+ archive_file=DB11Nov2011_0605.tgz
$ echo $archive_file
+ echo DB11Nov2011_0605.tgz
DB11Nov2011_0605.tgz
$ set +x
+ set +x
$ echo $archive_file
DB11Nov2011_0605.tgz

# Backup the files using tar.
(cd /home/knoppix/backups/; tar czf $dest/$archive_file dbusers.txt)