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- Subject: Re: Lua Distributions and Package Management
- From: Ross Berteig <Ross@...>
- Date: Mon, 30 Sep 2013 14:09:08 -0700
On 9/28/2013 3:47 PM, Sean Conner wrote:
2. I was unaware that $HOME/bin was a common Unix idiom. And why are you
checking for $HOME/bin (or /usr/local/bin)?
Including $HOME/bin is (or was in the early 1980s) a common idiom among
Unix users. Where else would you put your personally written scripts and
programs on a timesharing system? Only the sysadmin had write access to
/usr/local, which itself was not necessarily present on early BSD and
System 3 Unix systems that I personally remember coming in contact with.
I remain surprised that convention does seem to have fallen into disuse
in Linux distributions. I guess it is no longer the case that a typical
user actually writes any scripts or programs of their own (as distinct
from installing things distributed as source), or if they do, they
habitually use sudo to copy them to /usr/local/bin. Personally, my shell
configuration always gets $HOME/bin added to my path.
3. I have an issue with your Windows version of an absolute path. On
Unix, '/' as the start marks an absolute path, but that's only because Unix
does not have the concept of drive letters. On Windows though, you have
which is a relative path to the current location. Then you have
which is an abolute path on the current drive, and then
No, just /.... is an absolute path on the current drive. With two
slashes, the path represents either a network file share (i.e.
//server/share/...), the internal device object namespace (i.e.
//./HardDisk0, //./COM10, or the like but by exceedingly strong
convention always specified with backslashes), and an escape mechanism
to support pathnames with unusual length or makeup (//?/....). This is
carefully documented at MSDN  but you have to parse the words carefully.
which is an absolute path on a particular drive.
Just C:/..., unlike Unix, doubling up the path separator is not
uniformly supported in Windows. It does work when doubled at any place
other than the start, but my reading of the docs indicates that is
incorrect even though it has been true as long as Windows and DOS have
supported directories at all.
Heck, that leads me to ask (since I don't have a Windows system to test this
valid? That is, relative to the current directory on the C: drive? I seem
to recall that MS-DOS kept track of the current directory on each drive.
Yes, that is valid. Windows keeps a separate current working drive for
each process, as well as a current working directory for each drive for
each process. The current drive and directories are inherited by child
processes in a generally sensible and obvious way.
 Yes, that *IS* a valid path in Windows. The Windows kernel does not
care if you use '/' or '\' as a path separator and will happily
accept both. It's just the default Windows command line that
bitches, and only because Windows (and MS-DOS, the precursor to
Windows) used '/' to mark command line options .
Valid though it may be, Windows users are not encouraged to know that
there is a second choice. As a long time Windows developer, I'd argue
that permitting both slashes in file names really was a mistake. It has
led to a lot of complacency about path parsing in "portable" code that
has caused a lot of pain. I suspect that just making Windows be
different would have been less painful in the long run. Of course, if
the future could have been predicted in the 1980s, then making DOS
ignore CP/M, every DEC OS, and I believe IBM mainframe conventions to
follow Unix and use / for path names and not for command line options
would have been the best answer. But who would have predicted then that
Unix and descendants would still be a live, viable OS in 2013?
 INT 21H, function 37H, Get/Set Switch Character
It defaulted to '/' but could be changed.
I tried that once in DOS 3.2 after noticing the API existed. The
resulting user experience was unpleasant because even then there were
just enough assumptions made by other tools. And changing it broke every
BAT file that used / for options. I put it back.
Ross Berteig Ross@CheshireEng.com
Cheshire Engineering Corp. http://www.CheshireEng.com/
+1 626 303 1602
+1 626 351 1590 FAX