From: Kristian Ivarsson <sten.kristian.ivarsson@gmail.com>
To: Ken Brown <kbrown@cornell.edu>
Cc: cygwin@cygwin.com
Subject: Re: TMP/TEMP environment variable and /tmp
Date: Fri, 18 Sep 2020 07:56:47 +0200 [thread overview]
Message-ID: <EA51058C-D017-4CCE-B207-C5EFD8CCC088@gmail.com> (raw)
In-Reply-To: <423c729e-4c66-dd5e-73c0-4c636089ea35@cornell.edu>
>>>>>>>> Does anyone know the rational with this behaviour and what can be
>>>>>>>> done to get hold of the (real) Windows TMP/TEMP
>>>>>>>> environment-variable-values (in a
>>>>>>>> (hopefully) platform independent way) ?
>>>>>>> so if you are making your custom tree, try to stick on that
>>>>>>> expectation and have both directories.
>>>>>> In general, you are free to set TMP to a directory of your choice,
>>>>>> that's the purpose of that variable, no need to sync it with some root.
>>>>>> There is a comment in /etc/profile:
>>>>>> # TMP and TEMP as defined in the Windows environment
>>>>>> # can have unexpected consequences for cygwin apps, but it does not
>>>>>> explain what consequences that might be; probably some trouble with
>>>>>> ACL/access permissions for temporary files.
>>>>> Nowadays that would be $LOCALAPPDATA/Temp, or if you really insist, the
>>>>> content of /proc/registry/HKEY_CURRENT_USER/Environment/TMP (or TEMP),
>>>>> after similarly expanding environment variable references found in that.
>>>>>
>>>>> The fact that getting Windows' idea of the user's TEMP directory is not
>>>>> immediately platform independent may well have been part of the rationale
>>>>> for not even trying that.
>>>>
>>>> Well, at least it's up to the user
>>>>
>>>> If the user sets its TMP-variable to "C:\Jabba Dabba Dooo" or "/jabba dabba doo", I expect the value of getenv("TMP") should be just that and regardless of OS the value returned is whatever the variable is set to and not magically changed to "/tmp"
>>> Of course and that's not happening, no worries. The issue was that TMP is set in /etc/profile and not inherited from the Windows environment.
>> Well, where my Cygwin-compiled-application is running, there’s no Cygwin-installation and thus no /etc/profile so it cannot be set there (if /etc/profile is not a built in resource in every executable), so there must be some text-value inside the compiled executables used in some manner somehow
>
> There must be something going on in your environment that you haven't told us yet. I just tried the following test case:
>
> #include <stdio.h>
> #include <stdlib.h>
> int
> main ()
> {
> printf ("The value of TMP is %s\n", getenv ("TMP"));
> }
>
> In a Cygwin bash shell I get
>
> The value of TMP is /tmp
>
> Running the same executable under a Windows Command Prompt, I get
>
> The value of TMP is /c/Users/kbrown/AppData/Local/Temp
>
> So Cygwin converts TMP to a Posix path [*], but it doesn't change it to "/tmp".
>
> Ken
>
> [*] See environ.cc:303 for a list of environment variables that Cygwin converts.
Hmm, you’re right Ken
I tried this before taking off for a vacation and the Windows-TMP-variable is extracted
I now suspect that we maybe do have some logic that falls back to /tmp if the TMP-variable is NULL and perhaps the variable is NULL because we launch the process with CreateProcess and perhaps the environment-variables doesn’t get inherited then ?
The reason why we use CreateProcess from within a cygwin-application to create another cygwin-application (instead of fork or such) might seem weird, but it has its reasons
I need to confirm this after the vacation-trip or if someone already know if environment-variables “dissapear” if things such as CreateProcess are used ?
Best regards,
Kristian
next prev parent reply other threads:[~2020-09-18 5:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-16 8:51 sten.kristian.ivarsson
2020-09-16 11:04 ` marco atzeri
2020-09-16 11:12 ` Thomas Wolff
2020-09-16 19:27 ` Hans-Bernhard Bröker
2020-09-17 12:12 ` Sv: " sten.kristian.ivarsson
2020-09-17 15:23 ` Thomas Wolff
2020-09-17 21:07 ` Kristian Ivarsson
2020-09-17 21:55 ` Ken Brown
2020-09-17 23:58 ` Doug Henderson
2020-09-18 2:17 ` Ken Brown
2020-09-18 3:56 ` Brian Inglis
2020-09-18 5:56 ` Kristian Ivarsson [this message]
2020-09-18 13:15 ` Brian Inglis
2020-09-21 7:57 ` Sv: " sten.kristian.ivarsson
2020-09-20 7:20 ` Andrey Repin
2020-09-17 16:13 ` Ken Brown
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