Check whether a .out file is genuinely Mplus output
Source:R/mplus.R
dot-mplus_is_genuine_output.Rd.out is a very generic extension (also used for compiled Unix binaries,
generic tool logs, etc.), unlike .spv/.smcl which are unambiguously
SPSS/Stata-specific – so, unlike those formats, a .out found in a
repository is not safely assumed to be Mplus by extension alone.
Classification (data_classify_files()/.fixed_ext_type) still keys on
the extension so a .out is downloaded in the first place (content can't
be checked before it's fetched), but this content check runs AFTER
download to catch and reclassify a false positive – Mplus always prints
its own version banner as the file's first real line, so this is a cheap,
reliable real/not-real test.