I need a script to check if a process is running, and if so, do one thing, else do...

[Underpants]

I have a script on a server that needs to be executed every day. Some days the script takes longer than 24 hours to complete. Obviously, I don't want the script to run if the one that was spawned the day before is still going at it.


So, in pseudo code this is what I want....

if dailycopy.sh is running; then run send-email-that-says-job-is-still-running.sh else run dailycopy.sh

[Tibuda]

#!/bin/sh
if [ `pgrep dailycopy.sh` ]; then
./send-email-that-says-job-is-still-running.sh
else
./dailycopy.sh
fi

[Underpants]

pgrep! That's a handy trick! thanks!!!

[lswb]

The pgrep command can identify running processes by name, see man pgrep for the different options. You could also use a lock or flag file of some kind, i.e. something like



#!/bin/sh
if [ -e MyScriptIsRunning ]; exit;
else touch MyScriptIsRunning
fi

# Main body of your script here....

rm MyScriptIsRunning


With the 2nd approach you have to consider if the script can fail or exit before the file is deleted at the end, or what happens if there is a system crash while the script is running.

[Underpants]

I just set it up using the first prep method. that's a super slick utility. thanks for the help!

[Underpants]

Problem. This isn't working.

veeam-copy.sh is NOT running but "/home/gwik/email-veeam-is-still-running.sh" launches and then it exits.




#!/bin/sh

if [ 'pgrep veeam-copy.sh' ]; then
/home/gwik/email-veeam-is-still-running.sh
else
/home/gwik/veeam-copy.sh
fi

[Underpants]

There are some rsync commands in the veeam-copy.sh script. I'm not able to pin down a process that pgrep can use. I can't use "rsync" because I have other scripts running at the same time which would interfere with what I'm trying to do here.


What can I do?

[lswb]

Problem. This isn't working.

veeam-copy.sh is NOT running but "/home/gwik/email-veeam-is-still-running.sh" launches and then it exits.




#!/bin/sh

if [ 'pgrep veeam-copy.sh' ]; then
/home/gwik/email-veeam-is-still-running.sh
else
/home/gwik/veeam-copy.sh
fi

With the single quotes you have used inside the brackets, the pgrep... line is just being treated as a string, not a command. So the if test will always be true, since the bracketed expression is a non-empty string. You may have meant to use backquote characters ( ` ) which would work OK as when they are used around a command they return the standard output of the backquoted command. Using the form $(command) is equivalent to the older `command` style and has some advantages in use.

There are a few different forms that will work, probably the simplest is just

if pgrep veeam-copy.sh ; then

When pgrep finds a process that matches its argument, it exits with 0 which an if test regards as "true" when returned from a command. If pgrep does not find a matching process or there is some kind of error, it exits with a non-zero return value which an if test will evaluate as false when returned from a command.

[Underpants]

You're right about the single quote thing. That's just my bad copying the example the first responder made for me onto another machine.

Now onto the next problem:

Like I said, the "veeam-copy.sh" script contains an rsync command, and some email commands to send me a log file.

I can look at the system right now (the script is running) and ps -ax doesn't show veeam-copy.sh as a running process, but the rsync command DOES show as a running process, making it difficult (or impossible) to use the if/then thing I just fixed :)


Thoughts?

[Underpants]

You're right about the single quote thing. That's just my bad copying the example the first responder made for me onto another machine.

Now onto the next problem:

Like I said, the "veeam-copy.sh" script contains an rsync command, and some email commands to send me a log file.

I can look at the system right now (the script is running) and ps -ax doesn't show veeam-copy.sh as a running process, but the rsync command DOES show as a running process, making it difficult (or impossible) to use the if/then thing I just fixed :)


Thoughts?

OK. This is what shows in ps. sh ./veeam-copy.sh

how can I use pgrep with that?

[lswb]

OK. This is what shows in ps. sh ./veeam-copy.sh

how can I use pgrep with that?

Here's 2 ways:

1) put "#!/bin/sh" as the first line of your script, then
chmod +x veeam-copy.sh
to make the script executable without having to call it with sh. After that you can just run the script itself, as ./veeam-copy, or if it is on your path, without the ./ . Then you can just use pgrep to search for the veeam-copy process with
pgrep veeam-copy

2) use the -f option to pgrep, which will find a match on the full command line, not just the process name, so you could use the line
pgrep -f "veeam-copy" and it would find "sh ./veeam-copy.sh"

[Underpants]

You're my hero! I think I just learned the significance of the "#!/bin/sh" part.... woot

[lswb]

If you are interested in scripting IMHO the best online or downloadble guide is the Advanced Bash Scripting Guide by Mendel Cooper, available here:

http://tldp.org/guides.html