Generating systematic incremental numbered filenames in Bash

I have a random number of files with names as:

id_1000.txt
id_2000.txt
id_3000.txt
id_4000.txt

Note that the number of .txt files varies in different directories. For example, a directory may contain only one id_1000.txt (at least) or may contain any number of files with any higher number of digits.

To convert the random number of filenames in systematic incremental number, I used following script in a batch script:

setlocal enabledelayedexpansion
set /a count=1
for /f "tokens=*" %%a in ('dir /b /od *.txt') do (
 echo ren "%%a" "id_!count!.txt"
 set /a count+=1
)

The output for the above input would be:

ren "id_1000.txt" "id_1.txt"
ren "id_2000.txt" "id_2.txt"
ren "id_3000.txt" "id_3.txt"
ren "id_4000.txt" "id_4.txt"

It first detects the number of id_*.txt files are there in the current directory, and then changes to the higher number with normal count order: 1, 2, 3, 4, etc. and echo a line.

Although I tried to search for alternative commands for Ubuntu, I could not find any satisfactory result.

I am very new to the Linux shell, any help in this matter will be appreciated.

Thanks

Answer

shopt -s globstar
n=0
for a in **/*.txt; do 
        ((n++))
        mv "$a" id_$n.txt
done