On 8/7/19 1:19 PM, Corinna Vinschen wrote: > On Aug 7 13:08, Michael Haubenwallner wrote: >> On 8/7/19 4:33 AM, Brian Inglis wrote: >>> On 2019-08-06 09:20, Michael Haubenwallner wrote: >>>> using 'env -i' to create an empty environment, the SYSTEMROOT and WINDIR >>>> environment variables are preserved (or recreated): >>>> $ /usr/bin/env -i /usr/bin/env >>>> SYSTEMROOT=C:\Windows >>>> WINDIR=C:\Windows >>>> And with cygpath, there is the -A, -D, -H, -O, -P, -S, -W and even -F flags >>>> to query the values for various directories. >>>> Now what I've failed to find is how to query the value for the >>>> "SystemDrive" >>>> environment variable. >>>> The problem behind is that I'm using "vswhere.exe" to locate some Visual >>>> Studio >>>> environment from within some scripts run via 'env -i', causing vswhere.exe >>>> to >>>> create a directory named "%SystemDrive%" in the current working directory: >>>> So I better ensure the SystemDrive environment variable is set for >>>> vswhere.exe. >>>> Any ideas? >>> >>> There is a reg entry: >>> >>> $ head >>> /proc/registry/HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/SystemBootDevice; >>> echo >>> multi(0)disk(0)rdisk(1)partition(3) >>> >>> but how do you convert that to a device letter? >>> >>> SYSTEMDRIVE is a dynamic env var created at startup pointing to the boot >>> drive >>> letter. It is not instantiated anywhere else as far I could find. A number >>> of >>> low level reg entries use that env var. Only option is to pass it through: >> >> Heck, even CreateEnvironmentBlock() relies on SYSTEMROOT env var being set, >> otherwise returning things like ProgramData="%SystemDrive%\ProgramData". > > So, what does this have to do with Cygwin in case you clean out the > environment? This is nothing you want to do if you plan to start > a non-Cygwin executable.
I do prefer to have full control over the environment, recreating the needed vars from the registry or similar, because I did have too much troubles with polluted environment already. This also applies to setting up some wrapper around the MSVC toolchain, that provide the vswhere.exe helper these days. Actually I would have been fine it was obvious enough to locate SYSTEMDRIVE, much like SYSTEMROOT and WINDIR are available via cygpath, or reading other specific environment variable values from /proc/registry/. As SYSTEMROOT and WINDIR are preserved already, even if they are available via cygpath as well, also preserving SYSTEMDRIVE simply feels suitable here. And even more since I found this commit, which seems to intent the same: https://cygwin.com/git/gitweb.cgi?p=newlib-cygwin.git;a=commitdiff;h=1f99dd3ecf3252517363ec8f0fec4b0a95706f31 Anyway: If it is possible to map above SystemBootDevice registry value to SYSTEMDRIVE, I would be fine as well. Thanks! /haubi/ -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
