Request to add support for piping into `fish -c 'builtin'` for built-ins about fish-shell HOT 3 CLOSED

Duplicate of #5714

from fish-shell.

The reason these won't read from stdin in that case is because they only do when "directly redirected", to avoid confusion with being called with 0 arguments given on the commandline (e.g. string match foo $bar when $bar is empty).

So this will have to be a flag (tho there probably won't be for count because that currently has none, use wc instead).

from fish-shell.

Thanks faho. In the mean time, for anyone also having this issue, a not-so-UUOC will get you there:

$ echo "1 + 2" | fish -N -c "cat | math"
3
$ printf '%s\n' abc xyz abba zzz | fish -N -c "cat | string match '*b*'"
abc
abba

from fish-shell.