UNIX for Dummies Questions & Answers

Hi there again.
Having a little problem using the $? value to decided whether to execute further code.

Im using Grep as follows:

rsh vps-is1 -Cvps.1 p1 status | grep "(noa)"

If i then "echo $?" im getting an exit value of 0 wether it finds the string or not. I have changed the grep value to both strings that exist and done exist in the file and still get exit code of 0 from both,

Any ideas what im doing wrong???

I believe you are seeing the return code from rsh and not your command. I believe thats just the way rsh works.

Try using ssh, it is capable of returning the result from the command it runs.

first with rsh

Code:

# > rsh sf1n04 ls /etc/hosts
/etc/hosts
# > echo $?
0

# > rsh sf1n04 ls /etc/host
ls: 0653-341 The file /etc/host does not exist.
# > echo $?
0

no with ssh

Code:

# > ssh sf1n04 ls /etc/hosts
/etc/hosts
# > echo $?
0

# > ssh sf1n04 ls /etc/host
ls: 0653-341 The file /etc/host does not exist.
# > echo $?
2

Notice when I misspell /etc/hosts I get a return code other than zero from ssh but not rsh.

i get :

ssh: not found when i substitute rsh for ssh. I guess we dont have it on the box (im at work)...

I cant add tools to the box, would invalidate our support agreement with the supplier....

Is there any other way you can think of that i can check the line status (as per my code above) and execute additional code if i get a return status of "noa" without using the exit status of the grep command?

Not sure if you get what you want...

Code:

rsh vps-is1 -Cvps.1 p1 status | { grep "(noa)" ; echo $? ; }

seems to give the correct exit status now, why is that different from the previous code. Can you explain the syntax of the new code above for me please so i understand it properly?

Many thanks