Bash replace first 4 characters after tail -f

Question

I have a log-file as .txt where I want the first four characters to be replaced by **** or XXXX to anonymize the data.

I am running the following command:

tail -f file.txt

I know I can cut the first characters the following way:

tail -f file.txt | cut -c4-

But I would then like to insert four wildcard characters.

How can I achieve this?

Answer 1

echo 1234567890 | sed 's/..../****/'

Output:

****567890