为何Tcl 8.6中存在file tempfile却缺失file tempdir？

Great question! Let's break this down clearly:

• First off, file tempdir is a relatively new addition to Tcl — it was officially introduced in Tcl 8.7. That's why you won't find it in the 8.6 release at all; it simply didn't exist back when 8.6 was finalized.

• Before Tcl 8.7, developers who needed access to the system's temporary directory had to use workarounds. The most common approaches were:

  • Leveraging platform-specific environment variables:
    • On Unix-like systems (Linux, macOS), check $env(TMPDIR) first, fall back to /tmp if it's unset
    • On Windows, use $env(TEMP) or $env(TMP)
  • Using file tempfile indirectly to get the directory:

    # Generate a temporary file, then extract its parent directory
    set temp_file_handle [file tempfile]
    set temp_dir [file dirname $temp_file_handle]
    # Clean up the unused temp file if you don't need it
    file delete $temp_file_handle
    

• The Tcl core team added file tempdir in 8.7 to address this gap. It was a request from the community: having a dedicated, cross-platform command to get the temp directory is far more intuitive than relying on workarounds or platform-specific logic.

内容的提问来源于stack exchange，提问作者Andrei Pozolotin