Re: printf -u "$fd"?

[Koichi Murase]

2024年5月22日(水) 0:15 Zachary Santer <zsanter@gmail.com>:
> Additionally, I was hoping the discussion of having a way to make fds
> not CLOEXEC without a loadable builtin[3][4] would get some more
> attention.

I haven't followed the discussion in the original thread for multiple
coprocs, but you can remove CLOEXEC relatively easily [1]:

  # Requires Bash >= 4.0
  function remove-cloexec {
    local fd=$1
    if ((fd!=0)); then
      builtin eval -- "exec 0<&$fd $fd<&- $fd<&0" </dev/null
    else
      builtin eval -- "exec 1>&$fd $fd>&- $fd>&1" >/dev/null
    fi
  }

This uses Bash's behavior of removing CLOEXEC for standard streams
0,1,2. (This behavior is probably undocumented, but I haven't checked
the document carefully). Adding CLOEXEC is more complicated and
relying on some assumptions.

[1] 
https://github.com/akinomyoga/ble.sh/blob/59787ee5528a8489e78ba09f712ed4b1f5a8e62f/src/util.sh#L3208-L3215
[2] 
https://github.com/akinomyoga/ble.sh/blob/59787ee5528a8489e78ba09f712ed4b1f5a8e62f/src/util.sh#L3114-L3207

--
Koichi