Shell Programming and Scripting

Hi,

I've got problem with one bash scrip which can run for random time (12h+) and then segfault:

clusterapp[17029]: segfault at 00007fff23100d00 rip 0000003da22426b4 rsp 00007fff23100cd0 error 6
clusterapp[14659]: segfault at 00007fff45cc3f50 rip 0000003da22426b4 rsp 00007fff45cc3f20 error 6

bash script:

Code:

updateMaster() {
echo 10.100.123.11 > /tmp/master
sleep 5
updateMaster
}
updateMaster

Now, that's called from different script:

Code:

deamonToKeepMasterAlive() {

touch /tmp/updatemaster.sh
echo "updateMaster() {" > /tmp/updatemaster.sh
echo "echo $SRV > /tmp/master" >> /tmp/updatemaster.sh
echo "sleep 5" >> /tmp/updatemaster.sh
echo "updateMaster" >> /tmp/updatemaster.sh
echo "}" >> /tmp/updatemaster.sh
echo "updateMaster" >> /tmp/updatemaster.sh
chmod +x /tmp/updatemaster.sh

exec /tmp/updatemaster.sh &

}

Idea was to keep an file with fresh, max 5 sec, time stamp.
Yeah, it's simple and possibly I could do loop to run 11 times and be called from cron to make it for a minute but that was quicker (and it was Friday so there you go!)

But why it's segfaulting? Any ideas?

The other question (sorry) would be why ps lists this

Code:

exec /tmp/updatemaster.sh &

with the name of script which called that script?

Cheers
Chris


Everything updated.
[root@mv-mb1 ~]# cat /etc/issue
CentOS release 5.3 (Final)
Kernel \r on an \m

[root@mv-mb1 ~]# uname -a
Linux mv-mb1.mvg.local 2.6.18-128.1.16.el5 #1 SMP Tue Jun 30 06:07:26 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

Bash should never segfault on a script, even an invalid script. It could be memory errors, a corrupted bash executable, or just a bug in bash. Try upgrading it.

I'm sure: your script is problem.

But try this:

Code:

updateMaster() {
echo 10.100.123.11 > /tmp/master
}

while true
do
     updateMaster
     sleep 5
done

Thanks for advice! Yeah, I've done "while" loop today and there is no way that this script is called more than once (I've started it manually).

I'm still curious why segfault? What's wrong with simple "goto"?
Is it bad practice to call function within a function?

One more thing - how can I make updatemaster.sh standalone script? With it's own name in processes list?

Many thanks again for your time and input!

edit: forgot to mention that everything is updated, nothing else running, 2GB memory and very fast CPU...
random crashes as well! on 3 different machines!

Cheers
Chris

Can you run interactivly "sh -x" to see what's going on while running?

A shell script alone should never segfault no matter how incorrect it is. As such, I doubt specific lines of code are responsible. Either you have memory errors, or the shell has a bug, or ran out of memory.

It is kind of bad practice to call a function from itself recursively with no exit strategy, that is, no way a function can terminate without calling itself. That just eats memory forever since it gets called thousands of times but never, ever returns. But I wouldn't think it would run out of memory THAT quickly.[/QUOTE]