Executing a bash script upon file creation

Question

I am looking write a small bash script to, when launched, watch a directory for any newly created files. If a new file appears, I want its presence to trigger a second scrip

Answer 1

How about incron? It triggering Commands On File/Directory Changes.

sudo apt-get install incron

Example:

Where can be a directory (meaning the directory and/or the files directly in that directory (not files in subdirectories of that directory!) are watched) or a file.

can be one of the following:

IN_ACCESS           File was accessed (read) (*)
IN_ATTRIB           Metadata changed (permissions, timestamps, extended attributes, etc.) (*)
IN_CLOSE_WRITE      File opened for writing was closed (*)
IN_CLOSE_NOWRITE    File not opened for writing was closed (*)
IN_CREATE           File/directory created in watched directory (*)
IN_DELETE           File/directory deleted from watched directory (*)
IN_DELETE_SELF           Watched file/directory was itself deleted
IN_MODIFY           File was modified (*)
IN_MOVE_SELF        Watched file/directory was itself moved
IN_MOVED_FROM       File moved out of watched directory (*)
IN_MOVED_TO         File moved into watched directory (*)
IN_OPEN             File was opened (*)

is the command that should be run when the event occurs. The following wildards may be used inside the command specification:

$$   dollar sign
$@   watched filesystem path (see above)
$#   event-related file name
$%   event flags (textually)
$&   event flags (numerically)

If you watch a directory, then $@ holds the directory path and $# the file that triggered the event. If you watch a file, then $@ holds the complete path to the file and $# is empty.

Working Example:

$sudo echo spatel > /etc/incron.allow
$sudo echo root > /etc/incron.allow

Start Daemon:

$sudo /etc/init.d/incrond start

Edit incrontab file

$incrontab -e
/home/spatel IN_CLOSE_WRITE touch /tmp/incrontest-$#

Test it

$touch /home/spatel/alpha

Result:

$ls -l /tmp/*alpha*
-rw-r--r-- 1 spatel spatel 0 Feb  4 12:32 /tmp/incrontest-alpha

Notes: In Ubuntu you need to activate inotify at boot time. Please add following line in Grub menu.lst file:

kernel /boot/vmlinuz-2.6.26-1-686 root=/dev/sda1 ro inotify=yes