How to concatenate strings in a Windows batch file?

Question

I have a directory for which I want to list all the .doc files with a ;.

I know the following batch command echos all the files:

for /r %%i In (*.doc) DO echo %%i

But now I want to put them all in a variable, add a ; in between and echo them all at once.
How can I do that?

set myvar="the list: "
for /r %%i In (*.doc) DO <what?>
echo %myvar%

Answer 1

What about:

@echo off
set myvar="the list: "
for /r %%i in (*.doc) DO call :concat %%i
echo %myvar%
goto :eof

:concat
set myvar=%myvar% %1;
goto :eof

Answer 2

Based on Rubens' solution, you need to enable Delayed Expansion of env variables (type "help setlocal" or "help cmd") so that the var is correctly evaluated in the loop:

@echo off
setlocal enabledelayedexpansion
set myvar=the list: 
for /r %%i In (*.sql) DO set myvar=!myvar! %%i,
echo %myvar%

Also consider the following restriction (MSDN):

The maximum individual environment variable size is 8192bytes.

Answer 3

Note that the variables @fname or @ext can be simply concatenated. This:

forfiles /S /M *.pdf /C "CMD /C REN @path @fname_old.@ext"

renames all PDF files to "filename_old.pdf"