1;0 blazar@feather:~/tmp$ perl -e 'open F, ">foo.txt"; seek F, 2**30, 0; print F
 1'
1;0 blazar@feather:~/tmp$ ls -lh . ; du -sh .
total 12K
-rw-r--r-- 1 blazar blazar 1.1G Nov 16 10:22 foo.txt
16K     .
1;0 blazar@feather:~/tmp$ time cp foo.txt bar.txt && echo -e "\a"

real    0m2.357s
user    0m0.204s
sys     0m2.064s

1;0 blazar@feather:~/tmp$ ls -lh . ; du -sh .
total 24K
-rw-r--r-- 1 blazar blazar 1.1G Nov 16 10:22 bar.txt
-rw-r--r-- 1 blazar blazar 1.1G Nov 16 10:22 foo.txt
28K     .