Device IO can be either very cheap (e.g. NVMe esp gen5) or very costly (e.g. a network filesystem maybe capped 125 MiB/s {gigE}). Either before or after costly operations it can be interesting to know how well the OS has buffered the data to prevent future reads.
fpr [optional-params] [paths: string...]
File Pages Resident. Examine UNION of paths & optional delim-delimited input
file (stdin if "-"|"" & stdin not a tty). Eg., find -print0 | fpr -d\0. Like
util-linux fincore, but more Unix-portable & summarizing.
-f=, --file= string "" optional input ("-"|!tty=stdin)
-d=, --delim= char '\n' input file delimiter (0->NUL)
-e=, --emit= set(Emit) summary Stuff to emit: summary detail
util-linux has fincore, but often I just want summary information and this is
easy to compute in-program than as a wrapper program. Also, this program should
work fine on OS X or many BSDs where util-linux is probably not installed.