Another way of declaring variables in bash

zhjim · 05-04-2009, 03:57 AM

Hi folks,

I have a little bash script that greps some info out of a config file. The way I'm doing this is using a for loop

Code:

for i in name disk vif; do
        DUMMY=$(grep "^[::space::]*$i" $CONF)
        DUMMY=$(echo $DUMMY | cut -d = -f 2-)


        # Get middle of "
        DUMMY=$(echo $DUMMY | sed 's/^.*"\(.*\)".*$/\1/g')      #DUMMY=${DUMMY#*\"}; #DUMMY=${DUMMY%*\"}
        # Get middle of '
        DUMMY=$(echo $DUMMY | sed "s/^.*'\(.*\)'.*$/\1/g")      #DUMMY=${DUMMY#*\'}; #DUMMY=${DUMMY%*\'}
      
        {$i}=\${$DUMMY}
done

The part were I'm lost is the last line inside the loop "{$i}=\${$DUMMY}.
What I'm trying to do is to have the value of $DUMMY to be assigned to a variable with the name of contents of $i.
So in the end I should have three variables with the names of $names, $disk, $vif

Is this possible at all?

Thanks in advance
Zhjim

ChrisAbela · 05-04-2009, 04:25 AM

"$" is a meta character, you should no use as part of the varaible name, or else it gets confusing.

If it is "i" that you would like assign a value then I suggest:

i=$DUMMY

Note that you already assigned a value to i in the "for" line. So "i" is already assigned the vlaues of "disk" and "vif".

linterrogate · 05-04-2009, 04:46 AM

Quote:

Originally Posted by zhjim

Hi folks,

I have a little bash script that greps some info out of a config file. The way I'm doing this is using a for loop

Code:

for i in name disk vif; do
        DUMMY=$(grep "^[::space::]*$i" $CONF)
        DUMMY=$(echo $DUMMY | cut -d = -f 2-)


        # Get middle of "
        DUMMY=$(echo $DUMMY | sed 's/^.*"\(.*\)".*$/\1/g')      #DUMMY=${DUMMY#*\"}; #DUMMY=${DUMMY%*\"}
        # Get middle of '
        DUMMY=$(echo $DUMMY | sed "s/^.*'\(.*\)'.*$/\1/g")      #DUMMY=${DUMMY#*\'}; #DUMMY=${DUMMY%*\'}
      
        {$i}=\${$DUMMY}
done

The part were I'm lost is the last line inside the loop "{$i}=\${$DUMMY}.
What I'm trying to do is to have the value of $DUMMY to be assigned to a variable with the name of contents of $i.
So in the end I should have three variables with the names of $names, $disk, $vif

Is this possible at all?

Thanks in advance
Zhjim

how about writing a python script instead, using true associative arrays. Your script will work, but the array indexes must evaluate to numeric values

Kenhelm · 05-04-2009, 09:42 AM

Try using 'eval'

Code:

name=
i=name
DUMMY=abc

eval $i=\$DUMMY

echo $name
abc

gnashley · 05-04-2009, 12:18 PM

bash indirect substituttion:
${!i}=\${$DUMMY}

bigearsbilly · 05-04-2009, 04:07 PM

why not just have the config file as a shell script and source it?

Code:

name=blah
age=humbug

Code:

. config

ChrisAbela · 05-05-2009, 02:13 AM

You can also place them in .bash_profile (or .bashrc, depending on your distro)

# export NAME=blah
# export AGE=humbag

The possibilites are endless
Let it never be said that Linux Users do net get support :-).

zhjim · 05-11-2009, 08:57 AM

Thanks for all the input. Got it working with eval, but changed it a bit to work

Code:

for i in name disk vif; do
        DUMMY=$(grep "^[::space::]*$i" $CONF)
        DUMMY=$(echo $DUMMY | cut -d = -f 2-)


        # Get middle of "
        DUMMY=$(echo $DUMMY | sed 's/^.*"\(.*\)".*$/\1/g')      #DUMMY=${DUMMY#*\"}; #DUMMY=${DUMMY%*\"}
        # Get middle of '
        DUMMY=$(echo $DUMMY | sed "s/^.*'\(.*\)'.*$/\1/g")      #DUMMY=${DUMMY#*\'}; #DUMMY=${DUMMY%*\'}

        eval $i=$DUMMY

done

echo $name
echo $disk
echo $vif

Code:

# ./mkximg /etc/xen/apache
apache
phy:/dev/sdb2,sda1,w
ip=10.0.0.2

Now onward to get the real information out of the last to vars.

Quote:

Originally Posted by ChrisAbela

The possibilites are endless
Let it never be said that Linux Users do net get support :-)

That's why I'm loving this *little* OS

Cheers Zhjim