topic if statement error handling in Operating System - HP-UX

if statement error handling

himacs — Tue, 18 Oct 2011 10:05:38 GMT

count=`ps -ef | grep LIST_8i | grep -v grep|wc -l`
pid=`ps -ef|grep LIST_8i|grep -v grep|awk '{print $2}'`
if [ $count = 1 ]
then
lsnrctl stop LIST_8i >> ${log}
sleep 5
lsnrctl start LIST_8i >> ${log}
else
echo " "
lsnrctl start LIST_8i >> ${log}
fi 2>&1

The script restarts listener if count is equal to 1.

This script fails when 'lsnrctl stop LIST_8i ' code aborts due to some tns adapter error.
In this scenario i had to use kill -9 <pid>.

Now i want modify script like when 'lsnrctl stop LIST_8i ' fails and kill -9 <pid> works.

Please guide me how i can achieve this.

Regards
himacs

Re: if statement error handling

James R. Ferguson — Tue, 18 Oct 2011 12:12:43 GMT

Hi:

First, avoid matching what you don't want to match by using the UNIX95 (XPG4) 'ps' behavior. You can redirect both STDOUT and STDERR to your ${log} once with an 'exec'.

# cat ./dolistener
#!/bin/sh
MYPROC=LIST_8i
PID=$(UNIX95= ps -C -o pid= ${MYPROC})
exec 2>&1 >> ${log} #...redirect STDOUT & STDERR to ${log}
if [ -z ${PID} ]; then #...nothing found...
    lsnrctl start ${MYPROC}
    exit 0
fi
lsnrctl stop ${MYPROC}
if [ $? ] -ne 0; then
    kill -9 ${PID}
    exit 1
fi
sleep 5
lsnrctl start ${MYPROC}
exit $?

The use of UNIX95 is confined to the 'ps' command. This is done by writing 'UNIX95=' followed immediately by whitespace; followed by the command whose behavior we want to alter. The '-C' option of 'ps' matches a process's basename. You may need to change the MYPROC value to match.

The '-o pid=' says to return the PID of any process(es) found. The '=' notation says to suppress the header line that would otherwise appear.

Regards!

...JRF...

Re: if statement error handling

Dennis Handly — Tue, 18 Oct 2011 16:53:46 GMT

>avoid matching what you don't want to match by using the UNIX95 (XPG4) 'ps' behavior.

You have a few typos and improvements that you can go back and edit:

>PID=$(UNIX95= ps -C -o pid= ${MYPROC})

PID=$(UNIX95=EXTENDED_PS ps -C ${MYPROC} -opid=)

>if [ $? ] -ne 0; then

if [ $? -ne 0 ]; then

>You can redirect both STDOUT and STDERR to your ${log} once with an 'exec'.

I think your order should be:

exec >> ${log} 2>&1 #... redirect STDOUT & STDERR to ${log}

Re: if statement error handling

James R. Ferguson — Tue, 18 Oct 2011 17:05:53 GMT

Hi (again):

> Dennis: You have a few typos and improvements that you can go back and edit:

So you play golf? :-) Yes, I could shorten any of the '-o' +name toggles to drop the space.

You are correct, of course on the test for the return value and on the 'exec'. Aside from a quick syntax check (which didn't detect the wrongly written test, the code was "ok".

As for the UNIX95= versus UNIX95=EXTENDED_PS or UNIX95=whatever the reader should see our exchanges in this thread:

http://h30499.www3.hp.com/t5/System-Administration/ps-ef-appname-grep-v-grep-How-to-avoid-grep-v-grep-quot/m-p/4282537#M335670

I agree that your EXTENDED_PS highlights the intention, though if a semicolon is inadvertantly added, then the setting persists for more than the intended command line.

Regards!

...JRF...

Re: if statement error handling

Dennis Handly — Tue, 18 Oct 2011 17:13:15 GMT

>Aside from a quick syntax check (which didn't detect the wrongly written test, the code was "ok".

You failed the ps(1) semantic check. The "-C" and its parm were separated by the -o.

The other changes were the improvements. ;-)

Re: if statement error handling

James R. Ferguson — Tue, 18 Oct 2011 17:30:56 GMT

@Dennis Handly wrote:
You failed the ps(1) semantic check. The "-C" and its parm were separated by the -o.
The other changes were the improvements. ;-)

Oops! Thanks. ENOCOFFEE ...or not enough, clearly :-)

So for clarity, we have:

#!/bin/sh
MYPROC=LIST_8i
PID=$(UNIX95=EXTENDED_PS ps -C ${MYPROC} -opid=)
exec >> ${log} 2>&1 #...redirect STDOUT & STDERR to ${log}
if [ -z ${PID} ]; then #...nothing found...
    lsnrctl start ${MYPROC}
    exit 0
fi
lsnrctl stop ${MYPROC}
if [ $? -ne 0 ]; then
    kill -9 ${PID}
    exit 1
fi
sleep 5
lsnrctl start ${MYPROC}
exit $?

And in deference to you, I even used EXTENDED_PS ;-)

Regards!

...JRF...