How do you avoid over-populating the PATH Environment Variable in Windows?

This will parse your %PATH% environment variable and convert each directory to its shortname equivalent and then piece it all back together:

@echo off

SET MyPath=%PATH%
echo %MyPath%
echo --

setlocal EnableDelayedExpansion

SET TempPath="%MyPath:;=";"%"
SET var=
FOR %%a IN (%TempPath%) DO (
    IF exist %%~sa (
        SET "var=!var!;%%~sa"
    ) ELSE (
        echo %%a does not exist
    )
)

echo --
echo !var:~1!

Take the output and update the PATH variable in environment variables.

if you are using windows vista or higher, you can make a symbolic link to the folder. for example:

mklink /d C:\pf "C:\Program Files"

would make a link so c:\pf would be your program files folder. I shaved off 300 characters from my path by using this trick.

In case anyone's interested...

I find I never really need all those paths at once, so I create a bunch of "initialization" batch files which modify the path accordingly.

For example, if I wanted to do some C++ development in Eclipse, I would do:

> initmingw
> initeclipse
> eclipse

This is also handy for avoiding conflicts between executables with the same name (such as the C++ and D compilers, which both have a make.exe).

My batch files typically look like this:

@echo off
set PATH=C:\Path\To\My\Stuff1;%PATH%
set PATH=C:\Path\To\My\Stuff2;%PATH%

I find this approach relatively clean and have yet to run into any problems with it.

One way I can think of is to use other environment variables to store partial paths; for example, if you have

C:\this_is_a\long_path\that_appears\in_multiple_places\subdir1;
C:\this_is_a\long_path\that_appears\in_multiple_places\subdir2;

then you can create a new environment variable such as

SET P1=C:\this_is_a\long_path\that_appears\in_multiple_places

after which your original paths become

%P1%\subdir1;
%P1%\subdir2;

EDIT: Another option is to create a bin directory that holds .bat files that point to the appropriate .exe files.

EDIT 2: Ben Voigt's comment to another answer mentions that using other environment variables as suggested might not reduce the length of %PATH% because they would be expanded prior to being stored. This may be true and I have not tested for it. Another option though is to use 8dot3 forms for longer directory names, for example C:\Program Files is typically equivalent to C:\PROGRA~1. You can use dir /x to see the shorter names.

EDIT 3: This simple test leads me to believe Ben Voigt is right.

set test1=hello
set test2=%test1%hello
set test1=bye
echo %test2%

At the end of this, you see output hellohello rather than byehello.

EDIT 4: In case you decide to use batch files to eliminate certain paths from %PATH%, you might be concerned about how to pass on arguments from your batch file to your executable such that the process is transparent (i.e., you won't notice any difference between calling the batch file and calling the executable). I don't have a whole lot of experience writing batch files, but this seems to work fine.

@echo off

rem This batch file points to an executable of the same name
rem that is located in another directory. Specify the directory
rem here:

set actualdir=c:\this_is\an_example_path

rem You do not need to change anything that follows.

set actualfile=%0
set args=%1
:beginloop
if "%1" == "" goto endloop
shift
set args=%args% %1
goto beginloop
:endloop
%actualdir%\%actualfile% %args%

As a general rule, you should be careful about running batch files from the internet, since you can do all sorts of things with batch files such as formatting your hard drive. If you don't trust the code above (which I wrote), you can test it by replacing the line

%actualdir%\%actualfile% %args%

with

echo %actualdir%\%actualfile% %args%

Ideally you should know exactly what every line does before you run it.