`jq -Rr 'split(" ")[0]'`? That would easily take me three decades to memorize ;-).

for selecting the second column, PID, from `ps aux`,

    ps aux | awk '{print $2}'

works for me, as gawk's default $FS field separator treats runs of whitespaces as a single separation of fields ( https://www.gnu.org/software/gawk/manual/html_node/Field-Spl... ), quite similar to "standard" Open Group/POSIX awk ( https://pubs.opengroup.org/onlinepubs/9799919799/utilities/a... ).

    ps aux | jq -Rr 'split(" ")[1]'

on the other hand doesn't work here due to `ps aux` adding a variable number of spaces for formatting.

    ps aux | jq -Rr 'split("\\s+"; null)[1]'

seems to work though.