Linux

Just wanted to join party:

grep '' * --recursive -H --max-count=5 --include '*.csv'

Grep can search recursively, and prepend the filename to the matched lines, and limit the number of matches from each file. Combine all that, and you get a solution, only problem is that the filename is followed by a colon:

subdir/test2.csv:1
subdir/test2.csv:
subdir/test2.csv:2
subdir/test2.csv:3
subdir/test2.csv:4
test1.csv:1
test1.csv:2
test1.csv:3

so you'd need to replace that...

grep '' * -r -H -m5 --include '*.csv' | sed 's/:/,/'