rc.local and cron questions

wenberg · 07-30-2004, 06:21 PM

I can start programs on boot by putting commands in rc.local. My question is, how do start programs on boot under a different user other than root?

My second question is ... where can I get info on making a script that I can use in cron. I want it to check if a program is running, and if not ... run a program.

Thanks for any help.

Mephisto · 07-30-2004, 07:32 PM

Quick answer

su - <username> -c "<command>"

Longer answer read "man su" and also read "man chmod" and more specifically for "X" set user ID for execution.

For cron look in the /etc/cron.* directories, there might be a sample there. If not I am sure someone here could provide an example. Basically you could grep for the process and if it was not found start it.

win32sux · 07-31-2004, 10:46 AM

anybody know how to make that bash script??

the one that checks to see if something is running and starts something if it's not...

=)

320mb · 07-31-2004, 11:03 AM

Quote:

Originally posted by win32sux
anybody know how to make that bash script??

the one that checks to see if something is running and starts something if it's not...

=)

ya easy...........

http://www.tldp.org/LDP/Bash-Beginne...ers-Guide.html
http://www.ibiblio.org/pub/Linux/doc...tro-HOWTO.html

win32sux · 07-31-2004, 11:28 AM

okay, let me re-phrase the question:

can somebody please post an example script that checks to see if something is running and starts something if it's not???

win32sux · 07-31-2004, 12:52 PM

okay i'll use pseudo-code and hopefully someone can change this to a real bash script:

ps aux | grep example.bin | grep -v grep

if the command above gives any output, then example.bin is running, so let's just exit...

if the command above doesn't give any output, then example.bin isn't running, so let's run it...

Mephisto · 07-31-2004, 01:42 PM

Bash scripting is not really my strongpoint. That said a simple example would be

if ps -e | grep -q "<executable name>"; then
echo "executable already running"
else
<executable command>
fi

I usually have to tinker a bit before I get the script right though.

win32sux · 07-31-2004, 03:25 PM

Quote:

Originally posted by Mephisto
Bash scripting is not really my strongpoint. That said a simple example would be

if ps -e | grep -q "<executable name>"; then
echo "executable already running"
else
<executable command>
fi

I usually have to tinker a bit before I get the script right though.

awesome! thanks, man!

=)

i blended my piece with your script and got this:

Code:

#!/bin/sh
if /usr/bin/ps aux | grep example.bin | grep -qv grep; then
exit
else /usr/bin/example.bin
fi

it seems to work very well... what do you think??

i have a couple questions:

what's the "-e" option on "ps" do?? is it better to use that instead of "aux"??

would it be wise to put an ampersand at the end of line 4 to make sure the example.bin process goes to the background??

win32sux · 07-31-2004, 04:01 PM

i added a couple lines so that it will log whenever it confirms the process is running, and whenever it starts another process...

Code:

#!/bin/sh
if /usr/bin/ps aux | grep example.bin | grep -qv grep; then
/usr/bin/date >> /var/log/checker.log
echo "example.bin CONFIRMED" >> /var/log/checker.log
exit
else /usr/bin/example.bin
/usr/bin/date >> /var/log/checker.log
echo "example.bin INITIATED" >> /var/log/checker.log
fi

how can i log the date on the same line as "example.bin CONFIRMED/INITIATED"??

with the script above the log looks like this:

Code:

Sat Jul 31 15:59:49 EST 2004
example.bin INITIATED
Sat Jul 31 16:00:49 EST 2004
example.bin CONFIRMED
Sat Jul 31 16:01:49 EST 2004
example.bin CONFIRMED

SBing · 07-31-2004, 04:16 PM

Quote:

Originally posted by win32sux
what's the "-e" option on "ps" do?? is it better to use that instead of "aux"??

You can find out a lot about commands by just type '--help' after a command, try:

$ ps --help

You'll receive an output of (cropped):

-e all processes

For scripting it'll make little difference I believe.

Quote:

Originally posted by win32sux
how can i log the date on the same line as "example.bin CONFIRMED/INITIATED"??

Try replacing:

echo "example.bin CONFIRMED" >> /var/log/checker.log

with

echo `date` "example.bin CONFIRMED" >> /var/log/checker.log

You can customize how the date is outputted to your own chosen format, try:

$ date --help

for more details

Good luck!

win32sux · 07-31-2004, 04:24 PM

that worked great! thanks SBing!

Code:

#!/bin/sh
if /usr/bin/ps aux | grep example.bin | grep -qv grep; then
echo `/usr/bin/date` "example.bin CONFIRMED" >> /var/log/checker.log
exit
else /usr/bin/example.bin
echo `/usr/bin/date` "example.bin INITIATED" >> /var/log/checker.log
fi

win32sux · 07-31-2004, 04:32 PM

is it best to use entire paths or just the command?? why??

echo `date` "example.bin CONFIRMED" >> /var/log/checker.log

echo `/usr/bin/date` "example.bin CONFIRMED" >> /var/log/checker.log

Cedrik · 07-31-2004, 04:52 PM

That depends of the environment

try put echo $PATH >> /var/log/checker.log you will see if /usr/bin is into it, no needs to indicate /usr/bin/date, just date will do

Mephisto · 07-31-2004, 06:29 PM

In Linux ps -e might not make a difference, I didn't check. On Irix it does though. Since I bounce around a lot (Irix, AIX, QSH, and BSD, but predominently Linux) I tend to use commands that work relatively consistently across platforms. Thus the -e.

win32sux · 07-31-2004, 06:47 PM

Quote:

Originally posted by Mephisto
In Linux ps -e might not make a difference, I didn't check. On Irix it does though. Since I bounce around a lot (Irix, AIX, QSH, and BSD, but predominently Linux) I tend to use commands that work relatively consistently across platforms. Thus the -e.

just curious, what's QSH???