editors/heme - The NetBSD Packages Collection

Heme is a fast and portable console hex editor for unix systems.  It
has undo support (number of undo operations is only limited by
available memory), ability to fill a range of addresses with the
specified byte, ability to search for a single byte or character
string.

Offsets can be given in hexadecimal, octal or decimal.  There are two
editing modes: hex and ascii.  In hex mode you type hexadecimal digits
and in ascii mode you type characters.  In the ascii mode cursor is
automatically moved to the next byte after typing a character (this
behaviour is configurable for hex mode).