how to use shell script checking last changed time of a file
You can get the last modification time of a file with stat, and the current date with date. You can use format strings for both to get them in "seconds since the epoch":
current=`date +%s`last_modified=`stat -c "%Y" $file`Then, it's pretty easy to put that in a condition. For example:
if [ $(($current-$last_modified)) -gt 180 ]; then echo "old"; else echo "new"; fi
The syntax of this if statement depends on your particular shell, but the date commands don't. I use bash; modify as necessary.
if [ $(( $(date +%s) - $(date +%s -r <file>) )) -le 180 ]; then # was modified in last three minuteselse # was not modified in last three minutesfiThe +%s tells date to output a UNIX time (the important bit is that it's an integer in seconds). You can also use stat to get this information - the command stat -c %Y <file> is equivalent. Make sure to use %Y not %y, so that you get a usable time in seconds.