Экранирование в переменной для awk

#!/usr/bin/awk -f
BEGIN{
  print "ASS" }

(yarametov@whitedevil)-'--> i=`echo "{null=Test, 1=7.5.1}" | awk -F "=" {'print $3'} | awk -F "}" {'print $1'}`
(yarametov@whitedevil)-'--> echo $i
7.5.1

#!/bin/bash
i=$(echo "$1" | awk -F "=" {'print $3'} | awk -F "}" {'print $1'})
echo $i

line 3: 2=: command not found
1=7.5.1}

#!/bin/bash

i=$(echo "{null=Test, 1=7.5.1}" | awk -F "=" {'print $3'} | awk -F "}" {'print $1'})
echo $i

bash test.sh 
7.5.1

itaos@g565:/tmp$ cat ./test.sh 
#!/bin/bash
i=`echo "$1" | awk -F "=" {'print $3'} | awk -F "}" {'print $1'}`
echo $i
itaos@g565:/tmp$ ./test.sh "{null=Test, 1=7.5.1}"
7.5.1

 cat test.sh 
#!/bin/bash
i=$(echo "$1" | awk -F "=" {'print $3'} | awk -F "}" {'print $1'})
echo $i
(yarametov@whitedevil)-'--> bash  test.sh "{null=Test, 1=7.5.1}"
7.5.1