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digitalmars.D.learn - Getting environment variables?

reply Christopher Wright <dhasenan gmail.com> writes:
Hey all,

How do I get environment variables in a D program? I specifically want 
the path to a user's home folder.

Ta muchly.
Nov 22 2008
next sibling parent reply "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Sat, Nov 22, 2008 at 12:55 PM, Christopher Wright <dhasenan gmail.com> wrote:

 Hey all,

 How do I get environment variables in a D program? I specifically want the
 path to a user's home folder.

 Ta muchly.


In Tango, there's tango.sys.Environment
(http://www.dsource.org/projects/tango/docs/current/tango.sys.Environment.html)
which provides a nice interface to environment variables.

In Phobos, I think you have to use the C functions to get at
environment variables, but std.path.expandTilde can be abused to get
the home folder ;)
Nov 22 2008
parent reply Christopher Wright <dhasenan gmail.com> writes:
Jarrett Billingsley wrote:

 On Sat, Nov 22, 2008 at 12:55 PM, Christopher Wright <dhasenan gmail.com>
wrote:

 Hey all,

 How do I get environment variables in a D program? I specifically want the
 path to a user's home folder.

 Ta muchly.


 
 In Tango, there's tango.sys.Environment
 (http://www.dsource.org/projects/tango/docs/current/tango.sys.Environment.html)
 which provides a nice interface to environment variables.
 
 In Phobos, I think you have to use the C functions to get at
 environment variables, but std.path.expandTilde can be abused to get
 the home folder ;)


Thanks, that's exactly what I was looking for.

I thought (perhaps wrongly) C allowed you to declare main as taking a 
list of environment variables, which is why I asked here rather than 
Tango's forums. But D doesn't, so I probably should have asked at the 
library-specific forums.
Nov 22 2008
next sibling parent BCS <ao pathlink.com> writes:
Reply to Christopher,


 I thought (perhaps wrongly) C allowed you to declare main as taking a
 list of environment variables,


It does.
Nov 22 2008
prev sibling parent "Mark Fischer" <marqfischer yahoo.com> writes:
Better late than never...

On Sunday, 23 November 2008 at 02:28:30 UTC, Christopher Wright
wrote:
...

 I thought (perhaps wrongly) C allowed you to declare main as 
 taking a list of environment variables, which is why I asked


Indeed, on Unix { not POSIX } and Windows:

 From Wiki:
======================
Other platform-dependent formats are also allowed by the C and
C++ standards, except that in C++ the return type must always be
int;[3] for example, Unix (though not POSIX.1) and Microsoft
Windows have a third argument giving the program's environment,
otherwise accessible through getenv in stdlib.h:

int main(int argc, char **argv, char **envp);

Mac OS X and Darwin have a fourth parameter containing arbitrary
OS-supplied information, such as the path to the executing
binary:[4]
======================

Mark
~~~~
May 02 2013
prev sibling next sibling parent reply "Stewart Gordon" <smjg_1998 yahoo.com> writes:
"Christopher Wright" <dhasenan gmail.com> wrote in message 
news:gg9h3f$9uo$1 digitalmars.com...

 Hey all,

 How do I get environment variables in a D program?


std.c.stdlib.getenv
http://www.cplusplus.com/reference/clibrary/cstdlib/getenv.html


 I specifically want the path to a user's home folder.


Platform-dependent.

For Windows, you can use the concatenation of HOMEDRIVE and HOMEPATH, but I 
don't know under which versions of Windows these variables are actually set.

----------
import std.c.stdlib, std.string, std.stdio;

void main() {
    string homeDrive, homePath;
    homeDrive = toString(getenv("HOMEDRIVE")).dup;
    homePath = toString(getenv("HOMEPATH")).dup;

    writefln("%s%s", homeDrive, homePath);
}
----------

For Unix, I'm informed that the HOME environment variable does it.
http://unix.derkeiler.com/Newsgroups/comp.unix.programmer/2005-09/0092.html

HTH

Stewart.

-- 
My e-mail address is valid but not my primary mailbox.  Please keep replies 
on the 'group where everybody may benefit.
Nov 22 2008
parent reply novice2 <sorry noem.ail> writes:
     homeDrive = toString(getenv("HOMEDRIVE")).dup;
     homePath = toString(getenv("HOMEPATH")).dup;


don't forget, that D char[] is utf8 and windows char* is 8-bit chars, not utf8.
so you should import std.windows.charset and use toMBSz() as D->WindowsAPI and
fromMBSz as WindowsAPI->D string converter. for example:
homeDrive = fromMBSz(getenv("HOMEDRIVE")).dup;
Nov 23 2008
parent reply "Stewart Gordon" <smjg_1998 yahoo.com> writes:
"novice2" <sorry noem.ail> wrote in message 
news:ggbd96$2drl$1 digitalmars.com...

     homeDrive = toString(getenv("HOMEDRIVE")).dup;
     homePath = toString(getenv("HOMEPATH")).dup;


 don't forget, that D char[] is utf8 and windows char* is 8-bit chars, not 
 utf8.
 so you should import std.windows.charset and use toMBSz() as D->WindowsAPI 
 and fromMBSz as WindowsAPI->D string converter. for example:
 homeDrive = fromMBSz(getenv("HOMEDRIVE")).dup;


Under what setups can the drive letter be a non-ASCII character?

But according to my experiments, getenv works in the OEM encoding rather 
than the Windows encoding, so you'd need

    homePath = fromMBSz(getenv("HOMEPATH"), 1).dup;

If you want to make sure all Unicode characters are preserved, you're best 
off using the Windows API

    wchar[] wpath;
    wpath.length = GetEnvironmentVariableW("HOMEPATH", null, 0);
    GetEnvironmentVariableW("HOMEPATH", wpath.ptr, wpath.length);

Stewart.

-- 
My e-mail address is valid but not my primary mailbox.  Please keep replies 
on the 'group where everybody may benefit.
Nov 23 2008
parent reply novice2 <sorry noem.ail> writes:
 Under what setups can the drive letter be a non-ASCII character?


any non-english windows have folders, usernames, etc with non-ascii chars,
therefore this names presents in environment, registry, file API etc.


     wchar[] wpath;
     wpath.length = GetEnvironmentVariableW("HOMEPATH", null, 0);
     GetEnvironmentVariableW("HOMEPATH", wpath.ptr, wpath.length);


i am afraid that windows API named *W works with UCS2 string.
but D wchar[] is UTF-16. since UCS2 is some sort of subset of UTF-16, then your
code above is correct (then lvalue is D wchar[]).
but problems can appear in reverse situation - pass D wchar[] to windows API.

that is why utf strings in D annoy me - because all strings exchange
D<->WindowsAPI shoud be passed thru to-utf and from-utf convertion. other
programming languages works fine with windows, not required utf-support editors
etc. 
sorry for offtopic.
Nov 23 2008
parent reply John C <johnch_atms hotmail.com> writes:
novice2 Wrote:


 i am afraid that windows API named *W works with UCS2 string.
 but D wchar[] is UTF-16.


Wrong - Windows has used UTF-16 as native since Windows 2000.
Nov 24 2008
parent reply Christopher Wright <dhasenan gmail.com> writes:
John C wrote:

 novice2 Wrote:
 

 i am afraid that windows API named *W works with UCS2 string.
 but D wchar[] is UTF-16.


 
 Wrong - Windows has used UTF-16 as native since Windows 2000.


Actually, you're both right. UCS2 is UTF-16.
Nov 24 2008
parent "Denis Koroskin" <2korden gmail.com> writes:
On Mon, 24 Nov 2008 16:53:20 +0300, Christopher Wright  
<dhasenan gmail.com> wrote:


 John C wrote:

 novice2 Wrote:


 i am afraid that windows API named *W works with UCS2 string.
 but D wchar[] is UTF-16.


  Wrong - Windows has used UTF-16 as native since Windows 2000.


 Actually, you're both right. UCS2 is UTF-16.


No. A quote from Wikipedia:

"Because of the technical similarities and upwards compatibility from  
UCS-2 to UTF-16, the two encodings are often erroneously conflated and  
used as if interchangeable, so that strings encoded in UTF-16 are  
sometimes misidentified as being encoded in UCS-2."

"UTF-16 is the native internal representation of text in the Microsoft  
Windows 2000/XP/2003/Vista/CE; Qualcomm BREW operating systems; the Java  
and .NET bytecode environments; Mac OS X's Cocoa and Core Foundation  
frameworks; and the Qt cross-platform graphical widget toolkit."

"Older Windows NT systems (prior to Windows 2000) only support UCS-2."
Nov 24 2008
prev sibling parent reply torhu <no spam.invalid> writes:
Christopher Wright wrote:

 Hey all,
 
 How do I get environment variables in a D program? I specifically want 
 the path to a user's home folder.
 
 Ta muchly.


I think the 'correct' way on Windows is to use SHGetSpecialFolderPathA.

Something like this:

char[MAX_PATH] buf;
SHGetSpecialFolderPathA(null, buf.ptr, CSIDL_PERSONAL, false);
char[] dir = toString(buf.ptr);

or CSIDL_APPDATA, etc.
Nov 23 2008
parent Lars Ivar Igesund <larsivar igesund.net> writes:
torhu wrote:


 Christopher Wright wrote:

 Hey all,
 
 How do I get environment variables in a D program? I specifically want
 the path to a user's home folder.
 
 Ta muchly.


 
 I think the 'correct' way on Windows is to use SHGetSpecialFolderPathA.
 
 Something like this:
 
 char[MAX_PATH] buf;
 SHGetSpecialFolderPathA(null, buf.ptr, CSIDL_PERSONAL, false);
 char[] dir = toString(buf.ptr);
 
 or CSIDL_APPDATA, etc.


In tango this is available in tango.sys.win32.SpecialPath

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource, #d.tango & #D: larsivi
Dancing the Tango
Nov 23 2008