I'm running multiple 'shred' commands on multiple hard drives in a workstation. The 'shred' commands are all run in the background in order to run the commands concurrently. The output of each 'shred' is redirected to a text file, and I also have the output directed to the terminal as well. I'm using tail to monitor the log file for errors, and halt the script if any are encountered. If there are no errors, the script should simply continue on to conclusion. When I test it by forcing a drive failure (disconnecting a drive), it detects the I/O errors and the script halts as expected. The problem I'm having is that when there are NO errors, I cannot get 'tail' to terminate once the 'shred' commands have completed, and the script just hangs at that point. Since I put the 'tail' command in the 'while' loop below, I would have thought that 'tail' would continue to run as long as the 'shred' processes were running, but would then halt after the 'shred' processes stopped, thus ending the 'while' loop. But that hasn't been the case. The script still hangs even after the 'shred' processes have ended. If I go to another terminal window while the script is "hangiing," and kill the 'tail' process, the script continues as normal. Any ideas how to get the 'tail' process to end when the 'shred' processes are gone?
My code:
shred -n 3 -vz /dev/sda 2>&1 | tee -a logfile &
shred -n 3 -vz /dev/sdb 2>&1 | tee -a logfile &
shred -n 3 -vz /dev/sdc 2>&1 | tee -a logfile &
pids=$(pgrep shred)
while kill -0 $pids 2> /dev/null; do
tail -qn0 -f logfile | \
read LINE
echo "$LINE" | grep -q "error"
if [ $? = 0 ]; then
killall shred > /dev/null 2>&1
echo "Error encountered. Halting."
exit
fi
done
wait $pids
There is other code after the 'wait' that does other stuff, but this is where the script is hanging
