The rmt utility is used by the remote dump and restore programs in manipulating a magnetic tape drive through an interprocess communication connection. It is normally started up with an rcmd(3) call.
The rmt utility accepts requests specific to the manipulation of magnetic tapes, performs the commands, then responds with a status indication. All responses are in ASCII and in one of two forms. Successful commands have responses of:
A number \n
Number is an ASCII representation of a decimal number. Unsuccessful commands are responded to with:
.Xo Sy E Ar error-number
Error-number is one of the possible error numbers described in intro(2) and error-message is the corresponding error string as printed from a call to perror(3). The protocol is comprised of the following commands, which are sent as indicated - no spaces are supplied between the command and its arguments, or between its arguments, and \n indicates that a newline should be supplied: