Shell Programming and Scripting

What is the best way for a script to run to monitor a directory for the presence of files and then perform a function afterwords? I was hoping to have it continually run and sleep until it detects that files are present in the directory, then break out of the loop and go on to the next step.

What it does it waits for files to be transferred to it's local directory, then when the files are present it sftp's them out to another host. I already have the sftp script working just need the proper syntax for a loop to go to sleep until it detects the files in the directory. Also the file names and conventions will constantly change so I was hoping more for a 0 byte count compared to anything else besides a 0 byte count for a condition.This is a linux box using bash as the shell.

thanks in advance guys.

Classic mailbox problem. One problem you have is: how do you know the files are really there, as opposed to partly there? Also, after you sftp them out, do you remove them?

Without addressing these problems (above), here's a simple script:

Code:

MAILBOX=some_directory
seq=0
while true; do 
   let seq=seq+1   # this might be bash specific
   if  /bin/ls -1 $MAILBOX | grep ^ ; then
      # make sure incoming files aren't mixed up with files-to-be-processed
      mv $MAILBOX $MAILBOX.$seq
      mkdir $MAILBOX
      # your function
      sftp_this_directory $MAILBOX.$seq
      # clean up 
      rm -rf $MAILBOX.$seq
   fi

   sleep 300 # wait 5 minutes
done

One problem you have is: how do you know the files are really there, as opposed to partly there? Also, after you sftp them out, do you remove them?

Hello, thanks for the quick response! You have good points and this has been discussed. We do remove them after transfer. another note is that although the names will change as will the byte size, they will always end in *.dat. One of other problems is as you mention what if the files are detected before they are finished transferring to the host, before they are sent back out?

thanks

What is your if statement actually doing?

thanks

what about using the watch command?

thanks

also in your while statement, when would the condition not be true?
thanks

better yet create a script that runs "one" time to look for (ls) files and use lsof to add logic for files currently being written to, next add a function for what you want to do with files NOT being written to.

Place that script in a users (root?) cron that runs every minute.

example of logic using lsof:

for F in `ls`
do
VAL=`lsof /full/path/to/$F`
if [ -z $VAL ]
then
your_function_here $F
fi
done