Unable to modify PATH during installation

Trying to install SWI-Prolog for Windows 8.0.3 (64-bit) and I select to modify the PATH variable for all users. I get the error message:
“Warning! PATH too long installer unable to modify PATH!”
The installation is done, but I cannot use JPL for a Java->Prolog application.
Is there a way to manually modify the PATH variable afterwards? WHat is the correct path to be added?
Thank you

I recall this error but what exactly created the error? An install wizard, you trying to change the path or something else. A screen shot would be helpful. The reason I ask is because this problem is common on Windows but not limited to installing SWI-Prolog and a screen shot would help others who find this.

Based on the info given my guess is that the Windows user path environment variable is near its limit and by adding the path to SWI-Prolog to the user path environment variable, you caused the limit to be exceeded.

You have a few choices.

  1. You don’t need SWI-Prolog path in the PATH variable to start or use SWI-Prolog; adding it to the PATH variable just makes it more convenient to start SWI-Prolog from a command line prompt. In other words you can start it from a command line by giving the full path, or what I prefer is to create a taskbar icon that starts SWI-Prolog when I click on it.



  1. You can increase the size for items in the PATH by referring to another variable that is used with PATH. Let me just give you the instructions and you will see.

For System variables add a new system variable that will extend the path, e.g. PATH_EXTENDED .

In Path add %PATH_EXTENDED% .

Now you have another 1024 characters for the path.

I tested this with C:\Program Files\swipl\bin under PATH_EXTENDED and it worked to open swipl.exe from the command line.


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See also https://github.com/SWI-Prolog/swipl-devel/issues/450

Thanks for the tip. It did not work though. Installer keeps saying that the the path is too long. The manual modification of the path worked fine.