IP check with shell script

bladez · #1 (**permalink**) 02-06-2009

hi guys ..newbie here i would like to create a simple script tat will detect wether the machine has IP or not ...

but it seems that my script doesnt really work it kept rebooting...

i set this script during boot so that it will check else it will reboot

it a shell script thou...

Code:

 
if [!`hostname -i`] then
       echo "System rebooting in 3s";
       sleep 3;
       reboot;
else
       echo "Your Current IP is : `hostname -i`";
       echo "Starting System in 3s";
       sleep 3;

But this end result was my system end up infinite loops of reboots

... hope someone can help me ... thx.

zaxxon · #2 (**permalink**) 02-06-2009

I guess this host is getting it's IP via dhcp? Assuming this maybe correct the problem why it didn't get an IP.

Also checking for an IP I would use ifconfig instead maybe.

pludi · #3 (**permalink**) 02-06-2009

At which point of the boot process did you insert your script? Before or after your NIC is brought up? Is there anything else that might reboot the system? Also, why do you reboot the whole system if it didn't get an IP instead of just restarting the DHCP client?

As for your test, I don't think that 'hostname' ever returns nothing as long as there's at least a Loopback available.

Code:

testbed:~ # ifconfig
eth0      Link encap:Ethernet  HWaddr 08:00:27:23:56:F8
          inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0
          [...]

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          [...]

testbed:~ # /etc/init.d/network stop
Shutting down network interfaces:
    eth0      device: Advanced Micro Devices [AMD] 79c970 [PCnet32 LANdone(rev 40)
Shutting down service network  .  .  .  .  .  .  .  .  .  .  .  .  .  done
testbed:~ # hostname -i
127.0.0.2
testbed:~ #

bladez · #4 (**permalink**) 02-09-2009

Yea i get IP via DHCP , well i am using D-Link switches with 24 pc's attached to it so sometimes som pc's doesnt get ip therefore i dun wan the pc to sit idle so at first yes i did thought of making it reboot but after i found the /etc/init.d/network start/stop i am gonna replace that with the reboot command instead so it will stop n start the NIC again untill it gets ip.

of course i did put this script after the NIC is started for the first time by the OS itself but then during the boot my script checks it to ensure it has IP n not jus loopback. coz i wanna ensure the pc is always on the network all the time.

there no other script that reboots the pc but the script that is below somehow something is wrong i dunno wat makes it keep restarting the network forever instead of checking whether it already has IP or not :

i hv a feeling that my code is wrong somewhr pls help... anyone..

..

Code:

 
 
if [!`hostname -i`] then
            /etc/init.d/network restart;
else
            echo "IP : `hostname -i`";
fi

Corona688 · #5 (**permalink**) 02-09-2009

First off, replace that restart with something else, really hard to debug anything when failure means your machine starts over. Have it print out the output of 'hostname' and 'hostname -i'.

bladez · #6 (**permalink**) 02-10-2009

i have found solution to it ... just to share it...

Code:

 
echo "Checking NIC status... Please Wait.";
host **Your Prefered WWW Address**>/dev/null
if [ $? -eq 0 ];
then
echo "Getting Client IP...";
sleep 3;
echo "Your IP : `ifconfig | gawk '/inet addr/{sub(".*:", "", $2);print $2; exit}'`";
else
echo "Re-initiating NIC...";
/etc/rc.d/init.d/network restart;
echo "Re-checking NIC Status...";
ping;
fi

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