More bash scripting help

[glennzo]

Something I don't understand although I've been browsing the typical bash scripting web sites. The following script simply tells me which computer it is being run on. There are 4 possibilities, the server, the phenom box, the centos box or the laptop. It works as expected. In the script there are two methods for achieving the desired result. I do believe that there are better ways to accomplish the task in a script but I don't know what these methods are referred to, arrays, loops, brace expansion, what? Seems that my code could be considered a bit redundant and could be shorter.

PHP Code:

#!/bin/bash
# Test if desktop or laptop

# Text strings
phenom="This is the Phenom Box"
server="This is the server"
centos="This is the CentOS Box"
laptop="This is the laptop"

if [[ $EUID -ne 0 ]] ; then                      # Need root permissions
   echo "Please execute this script with root permissions."
   exit 1
fi

function get_chassis()                           # Determine if system is desktop or laptop
{
chassis_type=$(dmidecode -s system-product-name)
if [[ $chassis_type == "N61PC-M2S" ]] ; then
   echo $chassis_type $phenom
else
   if [[ $chassis_type == "Satellite A205" ]] ; then
      echo $chassis_type $laptop
   else
      if [[ $chassis_type == "P4i65G" ]] ; then
         echo $chassis_type $centos
else
         if [[ $chassis_type == "P4V8X-MX" ]] ; then
            echo $chassis_type $server
         fi
      fi
   fi
fi
}
get_chassis

test_type=$(dmidecode -s system-product-name)
case $test_type in

"N61PC-M2S")
   echo $test_type $phenom
   ;;

"Satellite A205")
   echo $test_type $laptop
   ;;

"P4i65G")
   echo $test_type $centos
   ;;
"P4V8X-MX")
   echo $test_type $server
   ;;

esac 


So you can see that I've used if-then-else excessivly and I've also tried a case statement. I think it can be done with less code and in a way that makes more sense. Can anyone offer some help or a rewrite of this code?

Disclaimer: This is not a homework project. It's been almost 40 years since I've had to do homework

Edit: As an afterthought, I don't really want someone to rewrite the code for me. I just need to be pointed in the right diretion. "Glenn, you need to use <what?>"

[[ "N61PC-M2S", "Satellite A205", "P4i65G", "P4V8X-MX" ]]

[flyingfsck]

Uhmmm, why not just use the hostname?

[glennzo]

That would work too but wouldn't it amount to the same thing I'm doing with dmidecode?

[jpollard]

You can consider using an associative array - something like

#!/bin/sh

declare -A tbl
tbl['N61PC-M2S']='This is the Phenom Box'
tbl['Satellite A205']='This is the server'
tbl['P4i65G']='This is the CentOS Box'
tbl['P4V8X-MX']='This is the laptop'

echo ${tbl['Satellite A205']}

where my subscript in the echo is replaced with the dmidecode command.

[Skull One]

Using parameter expansion:

#!/bin/sh

N61P='This is the Phenom Box'
Sate='This is the server'
P4i6='This is the CentOS Box'
P4V8='This is the laptop'

type=$(dmidecode -s system-product-name)
echo $type $!${type:0:4}

Could you tell if it works? I have not tested it.

[stevea]

Nah associative array, as JP suggests are the right thing .... but we can tighten that up a little

$ declare -A tbl=(["4313CTO"]="my Laptop" ["H57M-USB3"]="My Server")
$ echo ${tbl["$(sudo dmidecode -s system-product-name)"]}
My Server

[glennzo]

Thanks for the replies guys. I've tried all three suggestions. Here's the code with edits:

PHP Code:

#!/bin/bash
# jpollard
declare -A tbl
tbl['N61PC-M2S']='This is the Phenom Box'
tbl['Satellite A205']='This is the server'
tbl['P4i65G']='This is the CentOS Box'
tbl['P4V8X-MX']='This is the laptop'

chassis_type=$(dmidecode -s system-product-name ${tlb})
echo $chassis_type

# Skull One
N61P='This is the Phenom Box'
Sate='This is the server'
P4i6='This is the CentOS Box'
P4V8='This is the laptop'

type=$(dmidecode -s system-product-name)
echo $type $!${type:0:4}

# stevea
declare -A tbl=(["N61PC-M2S"]="Phenom" ["Satellite A205"]="Laptop" ["P4i65G"]="CentOS" ["P4V8X-MX"]="Server")
echo ${tbl["$(sudo dmidecode -s system-product-name)"]} 


Here are the results:
jpollard --- > P4V8X-MX
Skull One --> P4V8X-MX P4V8
stevea --> Server

This stuff works, or at the very least is close, so after I get home from work I'll be off to study the code(s) so that I will understand what they do. Thank you so much.

For all the documentation that is available it certainly can be tough to filter down to exactly what you are looking for.

[jpollard]

Using a number of different scripting languages helps.

bash has adopted several features of other languages, but not provided a good tutorial or documentation on them that is easy to find and use.

I knew hash tables were taken, but understanding hash tables only came from using awk and perl (and some LISP where they were first exploited).

But reading the bash manpage was not very clear.

for things I put into scripts (other than the simplest) I still use Perl.

[Skull One]

Damn! It does not expand!
Humm... how was is already? I did it once, but cannot remember... :'(

Edit:
You can still use the following:

#!/bin/sh

N61P='This is the Phenom Box'
Sate='This is the server'
P4i6='This is the CentOS Box'
P4V8='This is the laptop'

type=$(dmidecode -s system-product-name)
mach=${type:0:4}
echo $type $mach

But I am sure there is a more compact syntax, damn!

[glennzo]

Seems the simplest form is:

PHP Code:

type=$(dmidecode -s system-product-name)
echo $type 


Working on the laptop the result:
Satellite A205

Works as a one-liner too type=$(dmidecode -s system-product-name) ; echo $type

Of course, I'm still working on developing some sort of understanding of the code

Thank you guys for all your help.