Script Help Pse 1

[MarkThomo]

I need to write a ksh shell script that will allow me to input the name of 1 of the computers/printers on the school network and will return the IP address of that host, the script needs to access the /etc/hosts to get the information and if the host is not found in the /etc/hosts file then output a message that the hostname cannot be located.

I only have basic script writing skill and and help would be greatly appreciated

many Thanks

Mark

 

[MikeLacey]

Hi Mark,

Unix has got some good tools to do this kind of thing.

This is actually three jobs:

1 - search thru the file
2 - detect whether the host name is in there
3 - print JUST the IP address if it is
- print 'Not found' if it isn't

You can search through a file for some text with the 'grep' command, like this:
[tt]
grep host_name /etc/hosts
[/tt]
and, assuming that the string host_name is in the file, grep will print out any line containing the string you've specified.

You can tell if a unix command worked by examining its return code, if it worked it will be zero.

The return code is in $?

so you can tell if a grep found something like this:
[tt]
grep string file > /tmp/a_file 2>&1
if [[ $? eq 0 ]]
then
[tab]echo "found it"
else
[tab]echo "didn't find it"
fi
[/tt]

Next, and last - pick out the IP address from the output of grep

Easy one this - use awk

Awk is a complex utility that's difficult to learn completely, but it can do some simple things very easily

In the file /tmp/a_file that was created above (by grep) is a line like this:
[tt]
192.168.100.3[tab]holly
[/tt]
you just want the first bit, the ip address
like this:
[tt]
cat /tmp/a_file | awk '{print $1}'
[/tt]

That should give you all of the bits you need to put together to make a working script. Get back to us if you need help with any particular bit.

Regards
Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[aigles]

You can use this simple script shell.

#!/usr/bin/ksh
ip=$(grep $1 /etc/hosts | awk '{print $1}')
echo ${ip:-"not found"}