Bash Script

jcky · 11-15-2009, 04:45 AM

#!/bin/bash
# alive2.sh
# Checks to see if hosts 192.168.1.100-192.168.1.105 are alive
# Iterate through IP address
for n in {100..105};
do
host=192.168.1.$n
ping -c2 $host &> /dev/null
if [ $? = 0 ];
then
echo "$host is UP"
else
echo "$host is DOWN"
fi
done

What is the purpose of "if [ $? = 0 ];"?

I need your kind help.

；p

pixellany · 11-15-2009, 04:55 AM

"$?" is the return code from a command. "0" means the command executed successfully.

You could also do this:

Code:

if $(ping -c2 $host &> /dev/null); then
     do stuff
else
     do other stuff
fi

(Always use [code] tags to make code easier to read.)

stevenworr · 11-16-2009, 11:46 PM

I can't resist:

Code:

for n in {100..105}
do
    host=192.168.1.$n
    echo -n "$host is "
    ping -c2 $host > /dev/null 2>&1 && echo up || echo down
fi
done

pixellany · 11-17-2009, 07:54 AM

Quote:

Originally Posted by stevenworr

I can't resist:

Code:

for n in {100..105}
do
    host=192.168.1.$n
    echo -n "$host is "
    ping -c2 $host > /dev/null 2>&1 && echo up || echo down
fi
done

Nice!! (but take out the "fi")