inotifywatch usage

Hi..
I need to check a file if it is modified and will append that file into another file if so. 'inotifywatch' , should do the script, however when I tested the command :

inotifywait  -e modify  ~/test.txt --format '%w' |cat >test2.txt

then i modified test.txt from other console, seems inotify did the job, quit without any message (no error nor event report), and when i checked test2.txt, file was empty.
what i did wrong, help ?
edited : I'm using debian stretch on i386/32 bit

Thanks and regards

Use xargs to execute the cat.

Originally Posted by syg00 Use xargs to execute the cat.

Thanks, I tested it :

inotifywait  -e modify  ~/test1.txt --format '%w''%f' | xargs cat >>test.txt

still no output on test.txt
interestingly, if I tried with 'access' event instead of modify, then it behave as what I expect (test1.txt is appended to test.txt)

inotifywait  -e modify  ~/test1.txt --format '%w''%f' | xargs cat >>test.txt

The problem is I only want to change test.txt when test1 is written/modified.
Is 'modify' event not implemented on inotifywait debian ?

It depends on how test1.txt is written/modified. Here are all the events when you run the following command.

echo "hello" >> test1.txt

/tmp/test.txt OPEN /tmp/test.txt MODIFY /tmp/test.txt CLOSE_WRITE,CLOSE

But if you modify test1.txt using a text editor the modify event is not triggered but instead you get these.

/tmp/test1.txt OPEN /tmp/test1.txt ACCESS /tmp/test1.txt CLOSE_NOWRITE,CLOSE /tmp/test1.txt OPEN /tmp/test1.txt CLOSE_WRITE,CLOSE /tmp/test1.txt ATTRIB

The events above were from the command

inotifywait -m /tmp/test1.txt

Originally Posted by michaelk It depends on how test1.txt is written/modified. Here are all the events when you run the following command.

Ouch, well noticed. It definitely work using echo and cat,thanks
I plan to use php/web interface to modify the file, not sure if it will trigger event ?

Thank

If you are using a web php script to modify the file, what is the purpose of using inotifywait?

Yes, you should get a modify event if use standard PHP file commands to open,write,close.

Hi michaelk..php to write a single configuration file to make it user friendly, and inotify will further parsing it to triger script to restart services if the file is modified

regards

How about using entr instead of inotifywatch?

echo ~/test.txt | entr -s 'cat ~/test.txt >> test2.txt'

dugan, you find (and expose) some wonderful nuggets ...

Originally Posted by dugan How about using entr instead of inotifywatch? echo ~/test.txt | entr -s 'cat ~/test.txt >> test2.txt'

Perfect ! Thank you very much