Eval function

[conquersmile]

Hello,

Can anybody help me with eval function in unix, I have no idea about it and i want some help.

Regards,
Padma Swamy

 

[sbix]

Hi Padma, what's worrying in "eval"? I use "eval" sometimes because it's a little tricky.
The standard definition of eval is:
"The eval command can be used when you want the shell to reprocess the command line a second time."
I.E.
The following function converts a number from Decimale to Hexadecimal and puts the result in a variable which name is passed as an argument:
#
# Dec2Hex :
# Converts the number in $1 (0 - 255) to hex 2 digits notation and puts it in the var specified in $2
#
Dec2Hex () {
stringa=$1
conv="0123456789ABCDEF"
a=`expr $stringa / 16`
b=`expr $a \* 16`
if [ $a -eq 0 ];then
digit1="0"
posiz=`expr $stringa + 1`
digit2=`echo $conv|cut -c$posiz`
eval ${2}=$digit1$digit2;
return
fi
posiz=`expr $a + 1`
digit1=`echo $conv|cut -c$posiz`
if [ $b = $stringa ];then
digit2="0"
else
posiz=`expr $stringa - $b`
posiz=`expr $posiz + 1`
digit2=`echo $conv|cut -c$posiz`
fi
eval ${2}="$digit1$digit2";
return
}

Hope to be useful

 

[conquersmile]

Hi,

I am using it to assign a value to a variable, which is generated dyanmically.

Regards,
Padma Swamy

 

[sbix]

Well .. it should differ just a little from the use I did.
A little question for you:
I find the name Padma for the 1st time in Harry Potter )
Where you from?