bash script selecting variable based on command line parameter

Question

I have a bash script that starts like this:

#!/bin/bash
systemStateGlobalSystemState=.1.3.6.1.4.1.674.10909.1.200.10.1.2
systemStateChassisStatus=.1.3.6.1.4.1.674.10909.1.200.10.1.4
systemStateVoltageStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.12
systemStateTemperatureStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.24
systemStateMemoryDeviceStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.27
         systemStateChassisIntrusionStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.30
operatingSystemMemoryStatus=.1.3.6.1.4.1.674.10909.1.400.20.1.4

RESULT=$(/usr/local/nagios/libexec/check_snmp -H $1 -o $2 -c $3)
CODE=$(echo $RESULT | awk '{print $4}')

What I am trying to do is if someone for $2 command line parameter enters operatingSystemMemoryStatus how do I select the predefined value for it in the script? So where $2 above is referenced in RESULT, how do I get that command to use the .1.3.6.1.4.1.674.10909.1.400.20.1.4 value?

So if I entered

check_snmp 192.168.0.1 operatingSystemMemoryStatus public script

would do:

/usr/local/nagios/libexec/check_snmp -H 192.168.0.1  -o .1.3.6.1.4.1.674.10909.1.400.20.1.4 -c public

How can I accomplish this?

Possible duplicate of [How do I parse command line arguments in bash?](http://stackoverflow.com/questions/192249/how-do-i-parse-command-line-arguments-in-bash) — Avihoo Mamka, Jan 15 '16 at 19:21
Not a duplicate. That post does not show how to take command line params and assign a value based on an existing defined variable of the exact same name. — John, Jan 15 '16 at 19:39
You could use a associative array like in [this question](http://stackoverflow.com/questions/16553089/bash-dynamic-variable-names). — Corubba, Jan 15 '16 at 19:47

gilhad · Answer 1 · 2016-01-15T19:55:28.110

I think, you want to use indirect expansion like this:

#!/bin/bash
systemStateGlobalSystemState=.1.3.6.1.4.1.674.10909.1.200.10.1.2
systemStateChassisStatus=.1.3.6.1.4.1.674.10909.1.200.10.1.4
systemStateVoltageStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.12
systemStateTemperatureStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.24
systemStateMemoryDeviceStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.27
systemStateChassisIntrusionStatusCombined=.1.3.6.1.4.1.674.10909.1.200.10.1.30
operatingSystemMemoryStatus=.1.3.6.1.4.1.674.10909.1.400.20.1.4

echo "you are looking for ${!2} value"
RESULT=$(/usr/local/nagios/libexec/check_snmp -H $1 -o ${!2} -c $3)
CODE=$(echo $RESULT | awk '{print $4}')

and call it like that

./myscript 192.168.0.1 operatingSystemMemoryStatus public script

you are looking for .1.3.6.1.4.1.674.10909.1.400.20.1.4 value
<expected result, which I cannot simulate on my box>

in man bash you can read

   If the first character of parameter is an exclamation point (!), it introduces a level of variable indirection.  Bash uses the value of the variable  formed
   from  the  rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than
   the value of parameter itself.  This is known as indirect expansion.

Excellent. That did it. Thanks. Wish I could mark this as the answer to my question. Only lets me mark the response that another thread is my answer. — John, Jan 15 '16 at 19:58
You should see on top left (before the I think ...." arrow up, zero, arrow down and big V - if you click the V, it would make it the answer. Maybe i needs first up-vote it with arrow up (useful), I am not sure on that — gilhad, Jan 15 '16 at 20:15
@John - I think you need to wait a bit before you can accept it as the correct answer. Try checking back in a day or two. — alvits, Jan 15 '16 at 20:49
Also, while this answers your immediate question, the approaches in the other answers -- a switch statement, or an associative array -- are arguably better ways to achieve what you are trying to do. — tripleee, Jan 18 '16 at 10:53

score 1 · Answer 2 · answered Jan 15 '16 at 19:58

1

You can use an associative array to achieve this:

declare -A lookup=(['foo']='bar' ['x']='y')
echo "${lookup[foo]}" # Prints "bar"

answered Jan 15 '16 at 19:58

l0b0

55,365
30
138
223

Walter A · Answer 3 · 2016-01-21T20:35:14.117

Use a switch construction. I added a 3-letter alternative for all options:

case $2 in
   "gss"|"systemStateGlobalSystemState")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.2"
       ;;
   "scs"|"systemStateChassisStatus")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.4"
   ;;
   "vsc"|"systemStateVoltageStatusCombined")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.12"
   ;;
   "tsc"|"systemStateTemperatureStatusCombined")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.24"
   ;;
   "dsc"|"systemStateMemoryDeviceStatusCombined")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.27"
   ;;
   "isc"|"systemStateChassisIntrusionStatusCombined")
       check=".1.3.6.1.4.1.674.10909.1.200.10.1.30"
   ;;
   "sms"|"operatingSystemMemoryStatus")
       check=".1.3.6.1.4.1.674.10909.1.400.20.1.4"
   ;;
   *) echo "Invalid option $1"
   ;;
esac
echo "Use $check now"

I have just copied/pasted the values. Not the best way, you can introduce variables that will make comparing and updating values easier:

precheck=".1.3.6.1.4.1.674.10909.1"
systemcheck="200.10.1"
oscheck="400.20.1"
    case $2 in
       "gss"|"systemStateGlobalSystemState")
           check="${precheck}.${systemcheck}.2"
           ;;
       "scs"|"systemStateChassisStatus")
           check="${precheck}.${systemcheck}.4"
       ;;
       "vsc"|"systemStateVoltageStatusCombined")
           check="${precheck}.${systemcheck}.12"
       ;;
       "tsc"|"systemStateTemperatureStatusCombined")
           check="${precheck}.${systemcheck}.24"
       ;;
       "dsc"|"systemStateMemoryDeviceStatusCombined")
           check="${precheck}.${systemcheck}.27"
       ;;
       "isc"|"systemStateChassisIntrusionStatusCombined")
           check="${precheck}.${systemcheck}.30"
       ;;
       "sms"|"operatingSystemMemoryStatus")
           check="${precheck}.${oscheck}.4"
       ;;
       *) echo "Invalid option $1"
       ;;
    esac
    echo "Use $check now"

Thanks Walter. I'm done with this already and working, however your suggestion definitely warrants going back and trying. Stay tuned. — John, Jan 21 '16 at 18:46

bash script selecting variable based on command line parameter

3 Answers3