Determine if a file is writable by a Bourne script user
Contributed by Rex 
October 20, 2003 
Tagged: Bourne shell scripting
From a Bourne shell script (sh, ksh, bash, …), it is possible to test if a file exists and is writable by the user running the script.
if [ -w testfile ]
then
echo testfile is writable!
else
echo non writable...
fi