Linux: Send mail after a process id finishes or is

问题:

I want to be notified on my email after another user's process kills or finishes. I can identify another user's process by its process id or the name of the process appearing in "top" command.

In order to do the same I wrote the following script:

while true; do
  if ps -ef | grep -q 'process_name'; then
    sleep 1
  else
   echo "complete" | mail -s "process exiting" [e-mail]
  fi
done

However, I find that even after another user's process finishes or the other user kills his or her process, still I am not getting any notification or email. Can someone please help me with this a bit.

回答1:

The problem is most likely this check:

if ps -ef | grep -q 'process_name'; then

It will always be true. Why? Just run it directly on the command line without the -q to grep and it will be obvious:

$ ps -ef | grep 'process_name'
user    4550  3349  0 09:17 pts/0    00:00:00 grep --colour=auto process_name
$ echo $?
0

The above example shows that the grep will always be successful because it finds itself!

There are many ways to fix that. One way is to use pgrep instead of grep.

if pgrep 'process_name' > /dev/null; then

回答2:

Another common technique to prevent the grep process from matching itself is to surround one of the letters in the pattern with [], like this:

grep -q '[p]rocess_name'

If you know the process of, then you don't need grep at all, you can use the exit code of ps itself:

if ps -p pid &> /dev/null; then
    sleep 1

where pid is of course the process id.