batch file - loop to append strings to variable

Question

How come this keep replacing the variable with each data from the loop instead of appending it?

set ipList=
for /F %%i in (ips.txt) do ( set ipList=%ipLis%,%%i )

Answer 1

It's true you need delayed expansion. Another way:

setlocal ENABLEDELAYEDEXPANSION
set ipList=
for /F %%i in (ips.txt) do ( set ipList=!ipList!,%%i )

Note the '!' instead of '%%'. Also, there was a typo in your question, I suppose it should be %%ipList%% instead of %%ipLis%% (a 't' is lacking).