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ddcan read binary data from nonseekable file descriptors without potentially destroying unread data due to stdio buffering. See here for an example: etalabs.net/sh_tricks.htmlhead -c Ncallsreadand never goes beyond N. In NetBSD 5.1,head -ccallsgetc. In FreeBSD 7.4,head -ccallsfread.<>redirection operator (read-write, you can use the reading in place of seek if you want to write in the middle of the file).ksh93has seeking operators (>#((...))...).ddalso exposes O_DIRECT (etc.) to shell scripting, which I think is also unique.truncateallows truncating or extending files, thus eliminating another use ofdd.