[Arjen Markus] (14 March 2003) Many of my company's programs rely on the presence of environment variables. Sometimes because third-party packages do, sometimes to find our own configuration files, sometimes because the operating system uses them to find the shared/dynamic libraries. (See [Extending the DLL Search Path on Windows])

It has been a great sorrow to me that full-scale installation scripts are needed to make such simple things possible as extending the PATH variable under [Microsoft Windows] and that if you need to do it manually, you have to open any of a wildly varying collection of windows to achieve what you want. 
It seems so much simpler under [Unix]. And I have never had "out of environment space" issues there.

The other day, I suddenly realised that there is no need to set these variables in the arcane ways of Windows: just use a small Tcl script. Using [Tclkit] has additional advantages:

   * No need to install Tcl separately
   * No DOS box appearing 
  
So, instead of defining MYVAR and extending PATH in the System panel, or whatever it is called today, just do:

   set ::env(MYVAR) "Whatever"
   lappend ::env(PATH) "c:/myprogramdir"

   exec myprog.exe &

When the exec command completes, the script is ended and so is Tclkit. But my program is running ...

[MHo]: This is because the newly executed myprog.exe inherits the environment table from its parent process.
P.S.: You don't have to struggle with windows dialogs to manipulate the environment permanently; take a look at the '''setx.exe'''-Utility from the resource-kit.




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More on this subject appears in, for example, "[Setting environment variables with a script]", and the remarks
here [http://groups.google.com/group/comp.lang.tcl/browse_thread/thread/82508e683bfeae16] by [GWL]
and [Ralf Fassel].
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[[
[Arts and crafts of Tcl-Tk programming] - [Category Windows]
]]
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'''[tombert] - 2016-04-27 12:34:31'''

If one does not want to add a static library search path to the PATH environment variable, based on the above ''restart'' approach one can also do the following.
Check on which platform you are running: windows, 32 bit or 64 bit. Create the additional library path to search for (in the example below it is in the share/lib32 or share/lib64 sub-path of the executable). If the path is not found in the current PATH environment restart the whole script.

I build this code because of dependency issues with my tdbc::postgres compilation. In the lib32 and lib64 path I put the libpq, libintl-8 ... libs.

======
## add lib32/lib64 library search path to environment
if {$tcl_platform(platform) == "windows"} {
    if {$tcl_platform(pointerSize) == 4} {
        set libPath [file join [file dirname [file dirname [info nameofexecutable]]] share lib32]
    } else {
        set libPath [file join [file dirname [file dirname [info nameofexecutable]]] share lib64]
    }
    set found 0
    foreach path [split $::env(PATH) ";"] {
        set path [file normalize $path]
        if {$path == $libPath} {set found 1}
    }
    if {!$found} {
        append ::env(PATH) ";[file nativename $libPath]"
        exec [info nameofexecutable] [info script] &
        exit
    }
}
======