Playing around with sparse files

This article is sparse. ;)
I am changing it all the time, because I am still learning how to work efficiently with sparse files.
Or...how it works at all.

Here's an example, using bash:

root@fuji log]# echo $F
wtmp lastlog
[root@fuji log]# F="$F rpmpkgs"
[root@fuji log]# du -ak $F ; ls -ldh $F
232 wtmp
28 lastlog
12 rpmpkgs
-rw-r--r-- 1 root root 571k Mar 21 11:39 lastlog
-rw-r--r-- 1 root root 11k Mar 21 04:02 rpmpkgs
-rw-rw-r-- 1 root utmp 225k Mar 21 11:39 wtmp

'Lastlog' is definitly a sparse file: it occupies just 28 k-bytes in disk, but is actually seen as a 571 k-bytes (as 'ls' shows).