How can I load the contents of a text file into a batch file variable?

SetLocal EnableDelayedExpansion
set content=
for /F "delims=" %%i in (test.txt) do set content=!content! %%i

echo %content%
EndLocal

set content=
for /f "delims=" %%i in ('filename') do set content=%content% %%i

set content=
for /f "delims=" %%i in ('type text.txt') do set content=!content! %%i

for /f "tokens=1 delims=" %%i in (file.txt) do echo %%i

for /f "tokens=1 delims=" %%i in (file.txt) do call :part2 %%i
goto :fin

:part2
echo %1
::do further processing here
goto :eof

:fin

set FileContents=

@echo off
   copy SetFile.bat + %1 $tmp$.bat > nul
   call $tmp$.bat
   del $tmp$.bat