How to use variable as separator in awk?

Shell Programming and Scripting
1

can some give me a example ?
eg:
a=usb
I want to use variable "a" as separator

2

Your question can be interpreted several ways. The obvious answer is:

FS=a

If this isn't what you want, you'll need to give us some context.

3

Hello,

Here is an example for same.

Lets say we have saved an variable like as follows.
a="test1"

Example input file is as follows:

cat test1211
test test1 test2
singh test1 tet3
gurmeet test1 test4

Code is as follows:

awk -F"$a" '{print $1 OFS $2}' test121

Output will be as follows:

test   test2
singh   tet3
gurmeet   test4

Thanks,
R. Singh