А есть ли возможность при использовании hsh-run как-то отделить
stdout от stderr?

$ hsh-run -- ~/build find / -type f |wc -l
9660
$ hsh-run -- ~/build find / -type f |grep find:
find: /etc/tcb: Permission denied
find: /etc/default: Permission denied
find: /lib/modules: Permission denied
find: /var/lock/uucp: Permission denied
find: /var/lock/serial: Permission denied
find: /var/lock/subsys: Permission denied
find: /var/spool/mail: Permission denied
find: /var/nobody: Permission denied
find: /usr/lib/chkpwd: Permission denied
find: /usr/share/locale/pt_BR: Permission denied
find: /usr/share/locale/zh_CN: Permission denied
find: /usr/share/locale/zh_TW: Permission denied
find: /boot: Permission denied
find: /root: Permission denied
find: /.host: Permission denied
find: /lib64/modules: Permission denied
$ hsh-run -- ~/build find / -type f 2>/dev/null |wc -l
9660
$