Batch- string search on Windows PATH

I am writing an batch file in Windows to run post-installation scripts, and one of the things that needs to be done is to add a directory to the system path.

The script is working, and it does something like this:

setx Path "%PATH%;c:\path\to\add" -m

This is setting the path correctly, but this script could potentially be run multiple times if the user reinstalls the program.

I would like to search the string for c:\path\to\add so I don't keep adding the same path over and over to the system path. This is pretty trivial in Linux with sed, but I don't know what the command is in Windows. I've found findstr, but this seems to only work on files.

Is this possible in Windows without ins开发者_如何学编程talling additional software?

EDIT:

I'm using Inno Setup to create the install executable.

At the risk of some downvotes till an expert provides a sound way of doing this,
the below removes the specific path from the environment variable if it exists, so that it can be added again:

set str=%path%
:: str is the same with path

set str=%str:;C:\Path\To\Add=%
:: ";c:\path\to\add" is now removed from str

setx Path "%str%;c:\path\to\add" -m
:: proceed with setting the path

This carries the risk of removing the string if it is in fact actually a part of a path, for instance c:\path\to\add\somefolder. Also if the path actually ends with a \, or it is the first entry and it in fact does not start with ;, etc..

Various forms can be called consecutively to circumvent some of these,

set str=%str:;C:\Path\To\Add\;=;%
set str=%str:;C:\Path\To\Add;=;%
set str=%str:;C:\Path\To\Add\=%
set str=%str:C:\Path\To\Add\;=%
set str=%str:;C:\Path\To\Add=%

But, AAMOF I'n not sure this is a sane way of doing this..

This is my code snippet to find the "cvsnt" path in the PATH variable.

if not "x%PATH:cvsnt=%" == "x%PATH%" goto proceed
set PATH=w:\build-repository\cvsnt\2.5.03-2382;%PATH%
echo Path added
:proceed

The part to look at is

not "x%PATH:cvsnt=%" == "x%PATH%"

First I replace all occurrences of "cvsnt" with an empty string. The result is compared to PATH without replacement of "cvsnt". If they are not equal because of "cvsnt" was replaced then it exists in PATH and the code can proceed.

The starting x before %PATH% is only a placeholder to protect against certain "improper" starting characters. see Batch file: Find if substring is in string (not in a file)

The setx utility has a drawback, it can not handle variables longer than 1024 characters.

I have been wrote a script to handle cases longer than the limit and without a need to install anything. Answered the question here: Set environment variables with NSIS in Window 7

Instead of adding the path each time - you could check if the executable you are looking for can be found within the path using a command like this:

for %f in (cmd.exe) do if [%~$PATH:f]==[] setx Path "%PATH%;c:\path\to\add" -m

Make sure to check for /? to read more about the magic of %~$PATH:f.

This is a bit of a hackish workaround, but follows the logic you expect:

1. Search the PATH
2. Conditionally add to the PATH

It never removes anything from the PATH, so there's no fear of screwing up Windows by removing something accidently. Also, it checks the PATH variable directly, so you don't have to worry about another file with the same name that lives somewhere on the PATH.

echo %PATH% > myTmpPath.tmp
find /C /I "c:\path\to\add" myTmpPath.tmp
if %ERRORLEVEL% neq 0 setx PATH "%PATH%;c:\path\to\add"
del myTmpPath.tmp

I hate using temporary files, but it's quick and dirty, and probably safer than removing something from the PATH.

The third line is the only tricky one. Basically, this line tests the outcome of the FIND command above. Rob van der Woude states:

FIND returns an errorlevel of 1 or higher if the search string wasn't found.

He also explains:

Some executables return negative numbers for errorlevels! However, this can be fixed by using the following code to check for non-zero return codes:
IF %ERRORLEVEL% NEQ 0 ...