obtain a new variable out of "for statment"

3Gmobile · #1 (**permalink**) 08-08-2006

first i have pre-define some variable, then input those into a for statement for some process, finally, i want to get a new value out of it.

A=192.168.16.1
B=192.168.32.1
C=192.168.64.1

for i in A B C
do
echo $i | nawk -F. '{ if ($3 > 16 and < 32) ....something like that, then ( $i= 192.168.202.1) , if ($3>16 and < 64) , then $i =192.168.203.1)....}'

done

echo $A <-- now how can i get the new value for other part of the shell to use.
echo $B
echo $C

sorry for the middle process, because i still trying to figure it out how to write the condition statement inside it.... But first i need to find out whether i am in a wrong direction.

Many thanks !

tmarikle · #2 (**permalink**) 08-08-2006

Maybe not what you are expecting but it meets the requirement as I read it:
Note: this works with ksh and bash

Code:

{
    unset A B C
    A=192.168.16.1
    B=192.168.32.1
    C=192.168.64.1

    # Add "var=" so that the code has something to work with following nawk's work
    for i in A=$A B=$B C=$C
    do
        # Use eval to make assignemnt
        # ...this will translate into var=nawk's output
        eval ${i%%=*}=$(echo "${i##*=}" | nawk -F. '{
            if ($3 >= 16 && $3 < 32)
                print "192.168.202.1"
            else
                print
        }')
    done
    echo A=$A
    echo B=$B
    echo C=$C
}

Output:

Code:

A=192.168.202.1
B=192.168.32.1
C=192.168.64.1

This can also be done without using awk.

3Gmobile · #3 (**permalink**) 08-08-2006

could you help to explain what does it mean ??

${i%%=*}=$(echo "${i##*=}

thanks you !

tayyabq8 · #4 (**permalink**) 08-09-2006

Quote:

Originally Posted by 3Gmobile

could you help to explain what does it mean ??

${i%%=*}=$(echo "${i##*=}

thanks you !

${parameter%%pattern} and ${parameter##pattern} work in the same way but difference is that '%%' matches the end of the value of parameter and ## matches the begining of the value of pattern. Lets explain it with example.

In the first iteration, value of i is A=192.168.16.1, ${i%%=*} will match from the end of the value of i, until it finds '=' and will delete the matched pattern, so in this case it'll match '=192.168.16.1' and will delete it, yeilding 'A'.

${i##*=} will match from the begining of the value of i, until it finds '=' and will delete the matched pattern, so in this case it'll match 'A=' and will delete it, yeilding '192.168.16.1'

So ${i%%=*} will output 'A' and ${i##*=} will output '192.168.16.1'

Regards,
Tayyab

aigles · #5 (**permalink**) 08-09-2006

Another way to do the work :

Code:

{
    unset A B C
    A=192.168.16.1
    B=192.168.32.1
    C=192.168.64.1

    for i in A=$A B=$B C=$C
    do
       echo $i | IFS="=..." read Var f1 f2 f3 f4
       if   [ $f3 -gt 16 -a  $f3 -lt 32 ] ; then
          eval $Var=192.168.202.1
       elif [ $f3 -gt 16 -a $f3 -lt 64 ]  ; then
          eval $Var=192.168.203.1
       fi
    done
    echo A=$A
    echo B=$B
    echo C=$C
}

Jean-Pierre.

tmarikle · #6 (**permalink**) 08-09-2006

Quote:

Originally Posted by aigles

Another way to do the work :

Code:

{
    unset A B C
    A=192.168.16.1
    B=192.168.32.1
    C=192.168.64.1

    for i in A=$A B=$B C=$C
    do
       echo $i | IFS="=..." read Var f1 f2 f3 f4
       if   [ $f3 -gt 16 -a  $f3 -lt 32 ] ; then
          eval $Var=192.168.202.1
       elif [ $f3 -gt 16 -a $f3 -lt 64 ]  ; then
          eval $Var=192.168.203.1
       fi
    done
    echo A=$A
    echo B=$B
    echo C=$C
}

Jean-Pierre.

Yep, that will run faster (4x on my system) for a single line, I wasn't sure what the OP's original goal was for including awk but the general flow of his post's code indicates single lines of input.

Why did you specify three periods in the IFS assignment? Only one is necessary.

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