trouble getting .shrc to take

[Gary Aitken]

Having set my shell to either sh or bash,
I can't seem to get .shrc to take.
If I have a .shrc that looks like:

  PROMPT_DIRTRIM=3;   export PROMPT_DIRTRIM
  PS1=\\w$ ; export PS1

PS1 is not defined when I log in, and the prompt is set to the default instead.

If I do
  ./.shrc
nothing seems to change;
although executing the above commands from the shell itself works.

What am I missing?