On Sat, 15 Aug 2015 01:17:28 +0100 Simon Slavin <slavins at bigfraud.org> wrote:
> > BTW, Posix is almost silent on the question. It says TMPDIR will > > define the location of a temporary store, but not how. > > I'm okay if the documentation simply says something like ... > > For Darwin (Mac), it's always /tmp/ > For Linux, see the TMPDIR environment variable > For Windows see [whatever it is] Agreed, although IIUC it could be simpler than that, see next. > However I suspect things may be more complicated than that. For > instance, does .NET respect the OS's choice of temporary directory no > matter which OS it's running under ? I have no idea. What I'm suggesting is that there is no "OS's choice", really. There are a few functions in the C standard library, e.g. tmpfile(3), that may consult the environment. The variable's name varies by implementation. Some implementations, notably GNU's (if the documentation is correct), do not consult the environment. I would guess .NET is written atop the Win32 API and uses GetTempFileName or somesuch. That uses GetTempPath, whose return value is affected by TMP and TEMP. (https://msdn.microsoft.com/en-us/library/windows/desktop/aa364992 (v=vs.85).aspx). GetTempPath and tmpnam(3) on Windows both honor TMP, but the fallback policies differ. So it's not really a question of what the OS's choice is, because the *OS* offers no "temporary file" function. It's really a question of which library function is called, and how that function is implemented. But none of that matters unless those functions are used. An application -- or library, as in SQLite's case -- need not use them, which in any case aren't all that helpful. AIUI SQLite does *not* use those functions, but rather has its own way to determine where temporary files go. In that case the rule could be quite simple and OS-independent. For instance, 1. Use "SQLITE_TMPDIR" if defined 2. Use current working directory otherwise where the value is set by sqlite3_initialize and cannot be changed thereafter. --jkl
