I would like to have a shell scipt that runs infinitely and keeps checking status of a php script (say my.php) and restarts it if the script has terminated somehow. I have the idea to go for -
ps -aux | grep "my.php"
and then use the result of this to check the status and do accordingly. Thanks in advance.
You can simply say:
ps -aux | grep -q "my.php" || php -f my.php
The way it works is that grep -q will not output anything but will return an "OK" exit code if it found something. when it returns a "NOT OK" exit code, the part after the || ("or") gets executed (because of boolean short-circuit evaluation - look it up).
You also need to make sure that:
you run the new script in the background and detach it from your console so that your script can keep monitoring
when you run ps | grep sometimes ps also lists your grep and then the grep "greps itself", so you have to filter that out.
It should look something like this:
while true
ps -aux | grep -v grep | grep -q "my.php" || ( nohup php -f "my.php" & )
sleep 1
done
or some-such..
Another approach is, start your php-program in a loop:
for ((;;))
do
my.php
done
With Linux ps, you could use
ps -C "my.php"
instead of grep, to identify my.php. Grep commands often find themselves. Maybe your ps has a similar switch?
This ps conforms to: 1) Version 2 of the Single Unix Specification, 2) The Open Group Technical Standard Base Specifications, Issue 6, 3) IEEE Std 1003.1, 2004 Edition, 4) X/Open System Interfaces Extension [UP XSI], 5) ISO/IEC 9945:2003 - I thought that's enough.ps rather than SystemV options.If you DO really feel the need to grep the output of ps, beware of your grep finding itself.
[ghoti@pc ~]$ sleep 60 &
[1] 66677
[ghoti@pc ~]$ ps aux | grep sleep
ghoti 66677 0.0 0.0 3928 784 11 S 4:11PM 0:00.00 sleep 60
ghoti 66681 0.0 0.0 16440 1348 11 S+ 4:12PM 0:00.00 grep sleep
[ghoti@pc ~]$
There's an easy way to avoid this. Just make part of your grep into a more complex regular expression.
[ghoti@pc ~]$ sleep 60 &
[2] 66717
[ghoti@pc ~]$ ps aux | grep '[s]leep'
ghoti 66677 0.0 0.0 3928 784 11 S 4:11PM 0:00.00 sleep 60
ghoti 66717 0.0 0.0 3928 784 11 S 4:13PM 0:00.00 sleep 60
[ghoti@pc ~]$
On the other hand, if you just want to make sure that your PHP script always runs, you can wrap it in something that re-runs it when it dies:
while true; do
php /path/to/my.php
done
If you want this to run at startup, you can edit your crontab on the server, and use a @reboot tag, assuming you're using "Vixie" cron (common on Linux and BSD):
@reboot /path/to/wrapperscript
You can man crontab and man 5 crontab for more details on how to use cron and the @reboot tag.
pgrep, it's a whole lot easier to use.