bug#34488: Add sort --limit, or document workarounds for sort|head error messages

[Pádraig Brady]

On 25/02/19 22:35, Pádraig Brady wrote:
> Thanks for doing all that.
> I've attached a few changes:
> 
> - spelling fixes
> - usage() clarified/reordered
> - ensure sigset_t are initialized
> - Don't setprocmask() unless specified
> - Simplified SETMASK_SIGNAL_OPTION handling
> - The test missed `env` as a prerequisite
> - The test was slow/spun cpu, so used sleep instead of seq
> - Used $SHELL in case sh didn't support trap
> 
> I see that the last signal that `kill -l` lists is not included.
> I think we should be processing SIGNUM_BOUND also?

An additional patch attached to replace --list-signal-actions
with --list-ignored-signals.  This is simpler, and more symmetric
with the other options. Also the extra output was moot I think
since handlers are reset upon exec. For completeness the transitions are:

upon fork
  default -> default
  handled -> handled
  ignored -> ignored
  pending -> cleared
  blocked -> blocked

upon exec
  default -> default
  handled -> default
  ignored -> ignored
  pending -> pending
  blocked -> blocked

shell has additional rules:
  can't unignore
  handled -> default in subshell

I'll squash this into yours, before commit.

cheers,
Pádraig

env-list-ignored.patch
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