Protip: "sed -E 's/[0-9]+/N/g'" is, by itself, what I'd call 'unreasonably effective' at converting log lines into a canonicalized form, such that each line of

Protip: "sed -E 's/[0-9]+/N/g'" is, by itself, what I'd call 'unreasonably effective' at converting log lines into a canonicalized form, such that each line of printf or printf-equivalent source code corresponds to only one or a few distinct output lines. Then you can pipe it into "sort | uniq" (possibly "uniq -c" if you want counts, possibly for logspam-quantification purposes), and otherwise conceivably into a "profile" of a logfile, and then you can diff between a "normal" profile and something that may be less normal.