operator if
if [ ! -f not_file ]; then
# begin not(!) yes
else
# begin not no
fi
-b filename- Block special file
-c filename- Special character file
-d directoryname- Check for directory Existence
-e filename- Check for file existence, regardless of type (node, directory, socket, etc.)
-f filename- Check for regular file existence not a directory
-G filename- Check if file exists and is owned by effective group ID
-G filename set-group-id- True if file exists and is set-group-id
-k filename - Sticky bit
-L filename - Symbolic link
-O filename - True if file exists and is owned by the effective user id
-r filename - Check if file is a readable
-S filename - Check if file is socket
-s filename - Check if file is nonzero size
-u filename - Check if file set-user-id bit is set
-w filename - Check if file is writable -x filename - Check if file is executable
