is there really no standard UNIX filter that act likes "probabilistic cat", outputing one line or not with a given probability? (yes, i know it can be emulated with awk/perl oneliners, but still)
man shuf

@mike nope, shuf outputs all lines in a randomized order, which is now what the spec required here.

BTW, since that message I've implemented #stocat to address this and submitted it for inclusion into #moreutils: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=961638

#961638 - proposal: stocat - probabilistic cat - Debian Bug report logs