Fastest way to remove the first x characters from a very long string

[Grant Edwards]

On 2015-05-16, bruceg113355 at gmail.com <bruceg113355 at gmail.com> wrote:

> I have a string that contains 10 million characters.
>
> The string is formatted as:
>
> "0000001 : some hexadecimal text ... \n
> 0000002 : some hexadecimal text ... \n
> 0000003 : some hexadecimal text ... \n
> ...
> 0100000 : some hexadecimal text ... \n
> 0100001 : some hexadecimal text ... \n"
>
> and I need the string to look like:
>
> "some hexadecimal text ... \n
> some hexadecimal text ... \n
> some hexadecimal text ... \n
> ...
> some hexadecimal text ... \n
> some hexadecimal text ... \n"
>
> I can split the string at the ":" then iterate through the list
> removing the first 8 characters then convert back to a string. This
> method works, but it takes too long to execute.
>
> Any tricks to remove the first n characters of each line in a string faster?

Well, if the strings are all in a file, I'd probably just use sed:

$ sed 's/^........//g' file1.txt >file2.txt

or

$ sed 's/^.*://g' file1.txt >file2.txt