Interface to Unix utility functions
physical_ram ()
ram_limit_spec
command line arguments to set ram limits.
wrap_block_signals f
blocks all signals before execution of f
, and
restores them afterwards.
ensure_at_exit ()
: catch all signals, run at_exit functions,
then re-deliver the signal to self to ensure the default behavior.
at_exit functions are honored only when terminating by exit, not by signals,
so we need to do some tricks to get it run by signals too
get_ppids pid
returns the list of parent pids, up to init (1) for pid.