replace a string in huge file by incrementing with it number of appearance in file?

Question

I have a file of 500MB and it has strings :

  string_1 ..... string_500,

I need generate the copy of this file which has :

  string_501.......string_1000

I need to do this up to string_500000, what's the best way to solve this?

Answer 1

If it is literally as you describe, a constant string with variable suffixes then just generate the new file forgetting the old one.

If it's actually

wibble_1 something_2 that_3 changes_4 randomly_5

the I'd read and parse the thing in perl

Answer 2

If you just want to generate a sequence of strings (string_501 to string_500000), you can do this:

for i in `seq 501 500000`
do
    echo string_${i}
done