On 28 Jul 2015, at 9:55am, Paolo Bolzoni <paolo.bolzoni.brown at gmail.com> wrote:
> From the C interface, the way to decide the directory is setting the > value of sqlite3_temp_directory char pointer. As explained here: > https://www.sqlite.org/c3ref/temp_directory.html > This is also the first place sqlite3 checks. The documentation is clear: "Applications are strongly discouraged from using this global variable. It is required to set a temporary folder on Windows Runtime (WinRT). But for all other platforms, it is highly recommended that applications neither read nor write this variable. This global variable is a relic that exists for backwards compatibility of legacy applications and should be avoided in new projects." Also, sqlite3_temp_directory is accessed by the VFS level, by choice of the VFS. You might someday switch to another VFS which ignores it. > From anywhere else sqlite3 checks the value of those env variables: > SQLITE_TMPDIR, TMPDIR, TMP, TEMP, USERPROFILE. All uses of SQLite are 'the C interface'. That's all SQLite is: C code. The C code checks the above places, depending on which VFS you're using, which usually comes down to which OS you're using. The C code checks whatever environment variable the OS expects a user to use to set a default location for their temporary files. (It also checks a lot of other places, but it will definitely check whatever the documentation for the OS says is the correct environment variable.) Generally speaking you should let the computer's user or administrator set this variable, since they know which drives they have attached to the computer, and which one they want temporary files on. You're just a programmer of one application, running on a computer you've never seen. The exceptions are for embedded controllers, where the programmer is the administrator, and that on all platforms SQLite can create huge temporary files and some systems don't have that much space available for temporary files. Simon.
