date difference

Shell Programming and Scripting
1

if there are two date one is entered by user
and another is system date than how can we finds day difference
between these two date

try to make it within 4 lines

2

Answer
is
already
in the faq = 4 lines :smiley: http://www.unix.com/showthread.php?t=13785

3

how to file update in unix?