RMTOPS(3)

RMTOPS(3) | Library Functions Manual | RMTOPS(3)

# NAME

`rmtops` —
access tape drives on remote machines

# LIBRARY

Remote Magnetic Tape Library (librmt, -lrmt)

# SYNOPSIS

`#include <rmt.h>`
`#include <sys/stat.h>`

int
`isrmt`(int fd);

int
`rmtaccess`(char *file, int mode);

int
`rmtclose`(int fd);

int
`rmtcreat`(char *file, int mode);

int
`rmtdup`(int fd);

int
`rmtfcntl`(int fd, int cmd, int arg);

int
`rmtfstat`(int fd, struct stat *buf);

int
`rmtioctl`(int fd, int request, char *argp);

int
`rmtisatty`(int fd);

long
`rmtlseek`(int fd, long offset, int whence);

int
`rmtlstat`(char *file, struct stat *buf);

int
`rmtopen`(char *file, int flags, int mode);

int
`rmtread`(int fd, char *buf, int nbytes);

int
`rmtstat`(char *file, struct stat *buf);

int
`rmtwrite`(int fd, char *buf, int nbytes);

# DESCRIPTION

The `rmtops` library provides a simple means of transparently accessing tape drives on remote machines via rsh(1) and rmt(8). These routines are used like their corresponding system calls, but allow the user to open up a tape drive on a remote system on which he or she has an account and the appropriate remote permissions.

A remote tape drive file name has the form

`[user@]hostname:/dev/???`
where system is the remote system, /dev/??? is the particular drive on the remote system (raw, blocked, rewinding, non-rewinding, etc.), and the optional user is the login name to be used on the remote system, if different from the current user's login name.

For transparency, the user should include the file `<rmt.h>`, which has the following defines in it:

    #define access	rmtaccess
    #define close	rmtclose
    #define creat	rmtcreat
    #define dup	rmtdup
    #define fcntl	rmtfcntl
    #define fstat	rmtfstat
    #define ioctl	rmtioctl
    #define isatty	rmtisatty
    #define lseek	rmtlseek
    #define lstat	rmtlstat
    #define open	rmtopen
    #define read	rmtread
    #define stat	rmtstat
    #define write	rmtwrite

This allows the programmer to use open(2), close(2), read(2), write(2), etc. in their normal fashion, with the `rmtops` routines taking care of differentiating between local and remote files. This file should be included before including the file <sys/stat.h>, since it redefines the identifier ``stat'' which is used to declare objects of type struct stat.

The routines differentiate between local and remote file descriptors by adding a bias (currently 128) to the file descriptor of the pipe. The programmer, if he or she must know if a file is remote, should use `isrmt`().

# ENVIRONMENT

The RCMD_CMD environment variable can be set to the name or pathname of a program to use, instead of /usr/bin/rsh, and must have the same calling conventions as rsh(1).

# FILES

/usr/lib/librmt.a
  remote tape library

# RETURN VALUES

Several of these routines will return -1 and set errno to `EOPNOTSUPP`, if they are given a remote file name or a file descriptor on an open remote file (e.g., `rmtdup`()).

# SEE ALSO

rcp(1), rsh(1), rmt(8)

And the appropriate system calls in section 2.

# AUTHORS

Jeff Lee wrote the original routines for accessing tape drives via rmt(8).

Fred Fish redid them into a general purpose library.

Arnold Robbins added the ability to specify a user name on the remote system, the <rmt.h> include file, this man page, cleaned up the library a little, and made the appropriate changes for 4.3BSD.

Dan Kegel contributed the code to use the rexec(3) library routine.

# BUGS

There is no way to use remote tape drives with stdio(3), short of recompiling it entirely to use these routines.

The rmt(8) protocol is not very capable. In particular, it relies on TCP/IP sockets for error free transmission, and does no data validation of its own.

October 16, 2001 | NetBSD 10.1