Randomly select a line out of a text file and set that line as a variable

Question

How to randomly select a line/ip out of a text file, and set it as a variable.

I mean something like:

set IP=TheLine/IPFromOfTheFile

Answer 1

@echo off
setlocal EnableDelayedExpansion

rem Load file lines into "line" array
set "num=0"
for /F "usebackq delims=" %%a in ("theFile.txt") do (
   set /A "num+=1"
   set "line[!num!]=%%a"
)

rem Select one random line
set /A "rnd=%random% %% num + 1"
set "IP=!line[%rnd%]!"

echo %IP%

For further details on array management in Batch files, see this post.