grep -P '[\p{Han}]+' **/*.md -oh | tr -d '\s' > cat.log
-P 是正则表达式匹配
-h, --no-filename
Suppress the prefixing of file names on output. This is the default
when there is only one file (or only standard input) to search.
-o, --only-matching
Print only the matched (non-empty) parts of a matching line,
with each such part on a separate output line.