From the Coreutils info pages for head
(accessible through info coreutils 'head invocation'
):
For compatibility
head
also supports an obsolete option syntax-COUNTOPTIONS
, which is recognized only if it is specified first.COUNT
is a decimal number optionally followed by a size letter (b
,k
,m
) as in-c
, orl
to mean count by lines, or other option letters (cqv
). Scripts intended for standard hosts should use-c COUNT
or-n COUNT
instead.
This is why the syntax is equivalent. man head
doesn't tell you this, by the way.