mjhjmtu

I try to write script to check if a file was modified or not. If it did, it should echo "Error!", if not - script keeps running.

My script

#!/bin/bash
date=$(stat -c %y)$1
while true
 do date2=$(stat -c %y$1)
 if (date2 != date)
 echo "error!"
 done

Are there any errors?

you can use inotifywait , read more

inotifywait - wait for changes to files using inotify

inotifywait efficiently waits for changes to files using Linux's
inotify(7) interface. It is suitable for waiting for changes to files
from shell scripts. It can either exit once an event occurs, or
continually execute and output events as they occur.

use this command :

$ inotifywait -m -e modify /tmp/testfile

when i write into testfile , inotifywait alarm to me

e.g;

echo "bh" > /tmp/testfile

inotifywait show this message:

$ inotifywait -m -e modify /tmp/testfile
Setting up watches. 
Watches established.
testfile MODIFY 
testfile MODIFY 

also you can redirect output to while statement :

while read j
do
 echo "file changed"
 break
done < <(inotifywait -q -e modify /tmp/testfile)

filename="$1"

m1=$(md5sum "$filename")

while true; do

 # md5sum is computationally expensive, so check only once every 10 seconds
 sleep 10

 m2=$(md5sum "$filename")

 if [ "$m1" != "$m2" ] ; then
 echo "ERROR: File has changed!" >&2 
 exit 1
 fi
done

Consider using md5sum, is safer to check real file modifications. This is script will return "The files are different" if a file diverge from the other, but when you equalize then, it will say the files are equal again.

#!/bin/bash

loop1() cut -d' ' -f1)
 if [ "$md5f2" != "$md5f1" ]; then 
 echo "The files are different now." 
 #stop loop:
 break 
 fi
 done


loop2() cut -d' ' -f1)
 if [ "$md5f2" == "$md5f1" ]; then 
 echo "The files are equal again." 
 #stop loop:
 break 
 fi
 done


while true; do 
 loop1 "$1" "$2"
 loop2 "$1" "$2"
done

Save it as autocompare and run like:

./autocompare file1 file2 

If you do want to 'manually' check for change in the modification timestamp, as opposed to actual difference in the contents, you need:

• stat -c %y $1 consistently with the separating spaces and inside $( ... ). Even better, stat -c %y "$1" will work if your filename contains whitespace or any 'globbing' character




• test with classic [ ... ] or test ... and "$var" (because stat %y contains spaces; stat %Y would avoid that) or bash-enhanced [[ ... ]] which doesn't need quotes -- but not ( ... ) which does something completely different namely execute in a subshell




• some delay between loops so this doesn't completely hog your system

 #!/bin/bash 
 date=$(stat -c %y "$1")
 while sleep 1; do date2=$(stat -c %y "$1")
 if [[ $date2 != $date ]]; then echo "changed!"; break; fi
 # possibly exit [status] instead of break
 # or if you want to watch for another change, date=$date2
 done