Using the value of one variable to name another variable (in bash)

Shell Programming and Scripting
1

Hello all,

I'm working on a script, and as part of it, I'm trying to create a loop that will run through a stored piece of information a certain number of times pulling out information, and each time create a variable with a unique name that will store that information. I'm sure it's a simple syntax problem, but I've gone through it several different ways and I can't seem to find my mistake.

(05:15:30\[ddecosta@S.Man)
[~/bin]$ cat x
#!/usr/bin/bash

#Define Colours
red='\e[0;31m'
nc='\e[0m'

#Make certain that we have something to check
if [ -z $1 ];then
echo -e " ${red}You Must Specifiy what MOD you wish to check${nc}"
exit 1
fi

#Get QPSK info
lq=`listQpsk $1`
echo "Counting Number of DeMODS"
#Establish number of DeMods on QPSK 
num_of_mods=`echo "$lq"|awk '{print $3}'|grep -cw [1-9]`
#get current count for each DeMOD
modseq="1"
until [[ $modseq -gt $num_of_mods ]];do
count"$modseq"=`echo "$lq"|grep -w $modseq|awk '{print $5}'`
echo "$count"$modseq""
modseq=$(($modseq+1))
done

(05:15:17\[ddecosta@S.Man)
[~/bin]$ ./x 42
Counting Number of DeMODS
./x: line 40: count1=824: command not found
1
./x: line 40: count2=130: command not found
2
./x: line 40: count3=865: command not found
3
./x: line 40: count4=829: command not found
4
./x: line 40: count5=948: command not found
5
./x: line 40: count6=611: command not found
6
./x: line 40: count7=666: command not found
7
./x: line 40: count8=967: command not found
8


(05:15:36\[ddecosta@S.Man)
[~/bin]$

Just so you can see what the listQpsk value is:

(05:15:01\[ddecosta@S.Man)
[~/bin]$ listQpsk 42
 ID QPSK Name           Demod   IS2W    SignOn  % SignOn
--- ------------------  -----  -----  --------  --------
 42 SMANHUBAQPSK3          -       0         0        -
 42 SMANHUBAQPSK3          1     988       824        83
 42 SMANHUBAQPSK3          2     169       130        76
 42 SMANHUBAQPSK3          3    1014       865        85
 42 SMANHUBAQPSK3          4     971       829        85
 42 SMANHUBAQPSK3          5    1129       948        83
 42 SMANHUBAQPSK3          6     756       611        80
 42 SMANHUBAQPSK3          7     796       666        83
 42 SMANHUBAQPSK3          8    1201       967        80
--- ------------------  -----  -----  --------  --------
    Total (IS2W, signed on)     7024      5840        83
Jun 18 05:15:17 - listQpsk Ended.

All I want to do is set the 5th column of each line numbered 1-whatever as it's own variable (which will later be used to do some comparisons).

Thanks.

2

Well, you're using bash, and that has support for arrays (although older versions might not). Second, you can create variables using eval:

let x=10
eval x_$x=12
set|grep ^x
3

I appreciate the thought. I understand the idea of arrays, but I'm not really at the point where I can use them.

I'm trying to understand the eval command, but I'm not sure I'm getting it. I read through the man page and some examples on line...but it's not sinking in. But I've been up all night doing a maintenance, so I doubt I could understand much of anything right now.

4

About eval:

The bash shell process the command line by expanding variables and other "magic". After this is done, the line is now ready for processing by the command:

eval x_10=12

The eval simply executes the arguments as if those arguments had been the command itself. So bash executes:

x_10=12