Notes and gleanings.

• journalctl -k quietly means 'this boot only'
  2026-06-04

  journalctl -k implies -b, so a --since window over kernel logs silently shows only the current boot.

• Why signed (x*2)/2 folds to x but unsigned doesn't
  2026-06-04

  The same expression optimizes to a constant for signed ints and to real work for unsigned — because signed overflow is undefined, and one IR flag says so.

• d.get(k, default) is not d.get(k) or default
  2026-06-03

  The two forms answer different questions; "or default" fires on every falsy stored value, not on a missing key.

• which bash startup file runs, and when
  2026-06-02

  Login, interactive, and non-interactive bash each read different startup files — and ssh host cmd reads almost none of them.

• x is None, not x == None (and NaN isn't equal to itself)
  2026-06-01

  In Python use is for the singletons and == for values — and remember that NaN never compares equal to itself.