bash script for selecting a parameter from list of parameters

m4rtin · 12-21-2009, 02:19 AM

"snmpwalk -v 2c -c public 192.168.1.1 1.0.3.45.23.2.1" will print me a list(about 15 names, but may vary) of network interface names to stdout(most of those names ae multi word names). I would like to make a script, which puts a serial number(1,2,3,4,5,etc) before each interface name printed to stdout and then the script should wait for user input. The user input has to be one of those serial numbers and ENTER. Then this script will to something using this certain interface name. How to accomplish this in bash? Any example scripts?

catkin · 12-21-2009, 02:31 AM

Have you had any ideas or tried anything yet? LQ is more likely to help on seeing those -- and a sample list.

m4rtin · 12-21-2009, 03:03 AM

Quote:

Originally Posted by catkin

Have you had any ideas or tried anything yet? LQ is more likely to help on seeing those -- and a sample list.

yes, sorry. I have made this:

Code:

#/bin/bash

SNMPWALK=$(snmpwalk -v 2c -c public 192.168.1.1 ifAlias | sed 's/^.*\: //')

PS3="Choose: "
select i in $SNMPWALK quit
 do 
 [ $i = "quit" ]  && exit 0
 echo "You chose $i"
done

However, there are multiple-word interface names in it and 'select' makes those as different options. Is there a possibility to change this?

Disillusionist · 12-21-2009, 03:06 AM

What output does the snmpwalk command give?:

Code:

snmpwalk -v 2c -c public 192.168.1.1 ifAlias

and which parts of the output are you after?

m4rtin · 12-21-2009, 03:18 AM

Quote:

Originally Posted by Disillusionist

What output does the snmpwalk command give?:

Code:

snmpwalk -v 2c -c public 192.168.1.1 ifAlias

and which parts of the output are you after?

This:

Code:

snmpwalk -v 2c -c public 192.168.1.1 ifAlias | sed 's/^.*\: //'

will give me something similar:

Quote:

Customer1
Customer 2
Name 3 45
Interface eth0
blah blah

At the moment if I run this select script I get:

Quote:

1) Customer1
2) Customer
3) 2
4) Name
5) 3
6) 45
7) Interface
8) eth0
9) blah
10) blah
11) quit

but I would like to have:

Quote:

1) Customer1
2) Customer 2
3) Name 3 45
4) Interface eth0
5) blah blah
6) quit

Any ideas how to achieve this? Or is it possible at all using select?

colucix · 12-21-2009, 03:40 AM

You can try to pass the output of the snmpwalk command directly to the "in list", but previously you have to set the Input Field Separator (internal variable IFS) to a newline. This forces the shell to split the input fields not based on blank spaces, but on newlines only. Easier to show, than to explain:

Code:

#/bin/bash
#
#  Store the current IFS - default is <space><tab><newline>
#
OLD_IFS=${IFS}
#
#  Set IFS to newline
#
IFS="
"
#
#  Use "process substitution" to build the list for the select statement
#  See: http://tldp.org/LDP/abs/html/process-sub.html
#
PS3="Choose: "
select i in $(< <(snmpwalk -v 2c -c public 192.168.1.1 ifAlias | sed 's/^.*\: //')) quit
do 
  [ "$i" = "quit" ] && exit 0
  echo "You chose $i"
  break
done
#
#  Restore original IFS
#
IFS=${OLD_IFS}

Does this do the trick?

colucix · 12-21-2009, 03:58 AM

Just a note. I'm not sure, since I cannot reproduce your example, but maybe setting the IFS is enough and the process substitution is not really necessary. You can give it a try:

Code:

#/bin/bash
OLD_IFS=${IFS}

IFS="
"

SNMPWALK=$(snmpwalk -v 2c -c public 192.168.1.1 ifAlias | sed 's/^.*\: //')

PS3="Choose: "
select i in $SNMPWALK quit
do 
  [ "$i" = "quit" ] && exit 0
  echo "You chose $i"
  break
done

IFS=${OLD_IFS}

ghostdog74 · 12-21-2009, 04:58 AM

Code:

var=$( snmpwalk -v 2c -c public 192.168.1.1 ifAlias | awk -F": " '{
    a[++d]=$2
}
END{
    for(i=1;i<=d;i++){
        print i") "a[i]
    }
    printf "Choose: "
    getline choice < "-"
    echo $choice
}' )

echo $var

konsolebox · 12-21-2009, 06:16 AM

Just in case you don't want to use IFS or don't want to split a scalar variable using the command-line parser:

Code:

#!/bin/bash

exec 4< <(exec snmpwalk -v 2c -c public 192.168.1.1 ifAlias | sed 's/^.*\: //')

ITEMS=()

if [[ BASH_VERSION[0] -ge 4 ]]; then
	readarray -u 4 ITEMS
else
	while read -u 4 LINE; do
		ITEMS[${ITEMS[@]}]=$LINE
	done
fi

exec 4<&-

select A in "${ITEMS[@]}" quit; do
	[[ $A = quit ]] && break
	<do something with $A>
done

OR

Code:

...

ITEMS[$(( QID = ${#ITEMS[@]} ))]='Quit'

select __ in "${ITEMS[@]}"; do
	ID=$(( --REPLY ))

	[[ ID -eq QID ]] && break

	< do something with ${ITEMS[ID]} >
done

There's a reason why using the command-line to split a scalar variable may cause unexpected result. This is mostly when the string has a glob pattern. For example

Code:

VAR='1 * 2 3 4'
for A in $VAR; do
	echo "$A"
done

may output:

Code:

1
<some file(s)>
2
3
4

catkin · 12-21-2009, 09:41 AM

The bash select command would allow the user to choose by typing in a number rather than a string and would thus be easier on the user and less error prone.