I want to add a delimiter in some indexes for each line of a file.

I have a file with data:

```
10100100010000
20200200020000

```

And I know the offset of each column (2, 5 and 9)

With this sed command: `sed 's/\(.\{2\}\)/&,/;s/\(.\{6\}\)/&,/;s/\(.\{11\}\)/&,/' myFile`

I get the expected output:

```
10,100,1000,10000 
20,200,2000,20000

```

but with a large number of columns (~200) and rows (300k) is really slow.

Is there an efficient alternative?