Read $TMPDIR. If you are feeling generous, then check $TMP if $TMPDIR isn't set. On that note, you may also be interested in $XDG_RUNTIME_DIR (complex-ish sema

Read $TMPDIR. If you are feeling generous, then check $TMP if $TMPDIR isn't set. On that note, you may also be interested in $XDG_RUNTIME_DIR (complex-ish semantics) or $XDG_CACHE_HOME (Default: ~/.cache/)