182 lines
4.7 KiB
Groff
182 lines
4.7 KiB
Groff
.\" $NetBSD: rmtops.3,v 1.14 2010/03/22 22:00:37 joerg Exp $
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.\"
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.Dd October 16, 2001
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.Dt RMTOPS 3
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.Os
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.Sh NAME
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.Nm rmtops
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.Nd access tape drives on remote machines
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.Sh LIBRARY
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Remote Magnetic Tape Library (librmt, -lrmt)
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.Sh SYNOPSIS
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.In rmt.h
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.In sys/stat.h
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.Ft int
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.Fn isrmt "int fd"
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.Ft int
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.Fn rmtaccess "char *file" "int mode"
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.Ft int
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.Fn rmtclose "int fd"
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.Ft int
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.Fn rmtcreat "char *file" "int mode"
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.Ft int
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.Fn rmtdup "int fd"
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.Ft int
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.Fn rmtfcntl "int fd" "int cmd" "int arg"
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.Ft int
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.Fn rmtfstat "int fd" "struct stat *buf"
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.Ft int
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.Fn rmtioctl "int fd" "int request" "char *argp"
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.Ft int
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.Fn rmtisatty "int fd"
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.Ft long
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.Fn rmtlseek "int fd" "long offset" "int whence"
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.Ft int
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.Fn rmtlstat "char *file" "struct stat *buf"
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.Ft int
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.Fn rmtopen "char *file" "int flags" "int mode"
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.Ft int
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.Fn rmtread "int fd" "char *buf" "int nbytes"
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.Ft int
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.Fn rmtstat "char *file" "struct stat *buf"
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.Ft int
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.Fn rmtwrite "int fd" "char *buf" "int nbytes"
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.Sh DESCRIPTION
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The
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.Nm
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library provides a simple means of transparently accessing tape drives
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on remote machines via
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.Xr rsh 1
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and
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.Xr rmt 8 .
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These routines are used like their corresponding system calls, but
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allow the user to open up a tape drive on a remote system on which he
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or she has an account and the appropriate remote permissions.
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.Pp
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A remote tape drive file name has the form
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.Dl [user@]hostname:/dev/???
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where
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.Em system
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is the remote system,
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.Em /dev/???
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is the particular drive on the remote system (raw, blocked, rewinding,
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non-rewinding, etc.), and the optional
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.Em user
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is the login name to be used on the remote system, if different from
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the current user's login name.
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.\" .Pp
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.\" The library source code may be optionally compiled to recognize the
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.\" old
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.\" .Bx 4.2 ,
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.\" remote syntax
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.\" .sp
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.\" hostname[.user]:/dev/???
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.\" .sp
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.\" By default, only the first form (introduced in
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.\" .Bx 4.3 )
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.\" is recognized.
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.Pp
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For transparency, the user should include the file
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.In rmt.h ,
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which has the following defines in it:
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.Bd -literal
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#define access rmtaccess
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#define close rmtclose
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#define creat rmtcreat
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#define dup rmtdup
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#define fcntl rmtfcntl
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#define fstat rmtfstat
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#define ioctl rmtioctl
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#define isatty rmtisatty
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#define lseek rmtlseek
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#define lstat rmtlstat
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#define open rmtopen
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#define read rmtread
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#define stat rmtstat
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#define write rmtwrite
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.Ed
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.Pp
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This allows the programmer to use
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.Xr open 2 ,
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.Xr close 2 ,
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.Xr read 2 ,
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.Xr write 2 ,
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etc. in their normal fashion, with the
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.Nm
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routines taking care of differentiating between local and remote files.
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This file should be included
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.Em before
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including the file
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.Pa \*[Lt]sys/stat.h\*[Gt] ,
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since it redefines the identifier ``stat'' which is used to declare
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objects of type
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.Em "struct stat" .
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.Pp
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The routines differentiate between local and remote file descriptors
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by adding a bias (currently 128) to the file descriptor of the pipe.
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The programmer, if he or she must know if a file is remote, should use
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.Fn isrmt .
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.Sh ENVIRONMENT
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The RCMD_CMD environment variable can be set to the name or pathname
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of a program to use, instead of
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.Pa /usr/bin/rsh ,
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and must have the same calling conventions as
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.Xr rsh 1 .
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.Sh FILES
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.Bl -tag -width /usr/lib/librmt.a -compact
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.It Pa /usr/lib/librmt.a
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remote tape library
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.El
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.Sh DIAGNOSTICS
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Several of these routines will return \-1 and set
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.Va errno
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to EOPNOTSUPP, if they are given a remote file name or a file descriptor
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on an open remote file (e.g.,
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.Fn rmtdup ) .
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.Sh SEE ALSO
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.Xr rcp 1 ,
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.Xr rsh 1 ,
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.Xr rmt 8
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.Pp
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And the appropriate system calls in section 2.
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.\" .Sh CONFIGURATION OPTIONS
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.\" The library may be compiled to allow the use of
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.\" .Bx 4.2 -style
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.\" remote file names. This is not recommended.
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.\" .Pp
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.\" By default, the library opens two pipes to
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.\" .Xr rsh 1 .
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.\" It may optionally be compiled to use
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.\" .Xr rexec 3 ,
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.\" instead. Doing so requires the use of a
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.\" .Em .netrc
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.\" file in the user's home directory, or that the application designer be
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.\" willing to have
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.\" .Xr rexec 3
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.\" prompt the user for a login name and password on the remote host.
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.Sh AUTHORS
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Jeff Lee wrote the original routines for accessing tape drives via
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.Xr rmt 8 .
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.Pp
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Fred Fish redid them into a general purpose library.
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.Pp
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Arnold Robbins added the ability to specify a user name on the remote
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system, the
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.Pa \*[Lt]rmt.h\*[Gt]
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include file, this man page, cleaned up the library a little, and made
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the appropriate changes for
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.Bx 4.3 .
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.Pp
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Dan Kegel contributed the code to use the
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.Xr rexec 3
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library routine.
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.Sh BUGS
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There is no way to use remote tape drives with
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.Xr stdio 3 ,
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short of recompiling it entirely to use these routines.
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.Pp
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The
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.Xr rmt 8
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protocol is not very capable.
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In particular, it relies on TCP/IP sockets for error
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free transmission, and does no data validation of its own.
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