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Remote mag tape library from volume 18 of comp.sources.unix.

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This commit is contained in:
jtc 1996-08-09 03:35:17 +00:00
parent 6054b19d94
commit 67ead26177
4 changed files with 1188 additions and 0 deletions
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8
lib/librmt/Makefile Normal file
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LIB= rmt
SRCS= rmtlib.c
MAN= rmtops.3
NOPROFILE=
NOPIC=
.include <bsd.lib.mk>

18
lib/librmt/README Normal file
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README
This is the remote mag tape library. It allows a program that uses
Unix system calls to transparently use a file (usually a tape drive) on
another system via /etc/rmt, simply by including <rmt.h>. It is
particularly useful with tar and dd, and is supplied with GNU tar.
This package has evolved somewhat over the years. My thanks to the
people who did most of the original work, and those who've contributed
bug fixes; appropriate credit is in the man page and source files.
Enjoy,
Arnold Robbins
Emory U. Computing Center
arnold@emoryu1.cc.emory.edu
gatech!emoryu1!arnold
+1 404 727 7636

932
lib/librmt/rmtlib.c Normal file
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#ifndef lint
static char *RCSid = "$Header: /cvsroot/src/lib/librmt/rmtlib.c,v 1.1 1996/08/09 03:35:19 jtc Exp $";
#endif
/*
* $Log: rmtlib.c,v $
* Revision 1.1 1996/08/09 03:35:19 jtc
* Remote mag tape library from volume 18 of comp.sources.unix.
*
* Revision 1.7 89/03/23 14:09:51 root
* Fix from haynes@ucscc.ucsc.edu for use w/compat. ADR.
*
* Revision 1.6 88/10/25 17:04:29 root
* rexec code and a bug fix from srs!dan, miscellanious cleanup. ADR.
*
* Revision 1.5 88/10/25 16:30:17 root
* Fix from jeff@gatech.edu for getting user@host:dev right. ADR.
*
* Revision 1.4 87/10/30 10:36:12 root
* Made 4.2 syntax a compile time option. ADR.
*
* Revision 1.3 87/04/22 11:16:48 root
* Two fixes from parmelee@wayback.cs.cornell.edu to correctly
* do fd biasing and rmt protocol on 'S' command. ADR.
*
* Revision 1.2 86/10/09 16:38:53 root
* Changed to reflect 4.3BSD rcp syntax. ADR.
*
* Revision 1.1 86/10/09 16:17:35 root
* Initial revision
*
*/
/*
* rmt --- remote tape emulator subroutines
*
* Originally written by Jeff Lee, modified some by Arnold Robbins
*
* WARNING: The man page rmt(8) for /etc/rmt documents the remote mag
* tape protocol which rdump and rrestore use. Unfortunately, the man
* page is *WRONG*. The author of the routines I'm including originally
* wrote his code just based on the man page, and it didn't work, so he
* went to the rdump source to figure out why. The only thing he had to
* change was to check for the 'F' return code in addition to the 'E',
* and to separate the various arguments with \n instead of a space. I
* personally don't think that this is much of a problem, but I wanted to
* point it out.
* -- Arnold Robbins
*
* Redone as a library that can replace open, read, write, etc, by
* Fred Fish, with some additional work by Arnold Robbins.
*/
/*
* MAXUNIT --- Maximum number of remote tape file units
*
* READ --- Return the number of the read side file descriptor
* WRITE --- Return the number of the write side file descriptor
*/
#define RMTIOCTL 1
/* #define USE_REXEC 1 /* rexec code courtesy of Dan Kegel, srs!dan */
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#ifdef RMTIOCTL
#include <sys/ioctl.h>
#include <sys/mtio.h>
#endif
#ifdef USE_REXEC
#include <netdb.h>
#endif
#include <errno.h>
#include <setjmp.h>
#include <sys/stat.h>
#define BUFMAGIC 64 /* a magic number for buffer sizes */
#define MAXUNIT 4
#define READ(fd) (Ctp[fd][0])
#define WRITE(fd) (Ptc[fd][1])
static int Ctp[MAXUNIT][2] = { -1, -1, -1, -1, -1, -1, -1, -1 };
static int Ptc[MAXUNIT][2] = { -1, -1, -1, -1, -1, -1, -1, -1 };
static jmp_buf Jmpbuf;
extern int errno;
/*
* abort --- close off a remote tape connection
*/
static void abort(fildes)
int fildes;
{
close(READ(fildes));
close(WRITE(fildes));
READ(fildes) = -1;
WRITE(fildes) = -1;
}
/*
* command --- attempt to perform a remote tape command
*/
static int command(fildes, buf)
int fildes;
char *buf;
{
register int blen;
int (*pstat)();
/*
* save current pipe status and try to make the request
*/
blen = strlen(buf);
pstat = signal(SIGPIPE, SIG_IGN);
if (write(WRITE(fildes), buf, blen) == blen)
{
signal(SIGPIPE, pstat);
return(0);
}
/*
* something went wrong. close down and go home
*/
signal(SIGPIPE, pstat);
abort(fildes);
errno = EIO;
return(-1);
}
/*
* status --- retrieve the status from the pipe
*/
static int status(fildes)
int fildes;
{
int i;
char c, *cp;
char buffer[BUFMAGIC];
/*
* read the reply command line
*/
for (i = 0, cp = buffer; i < BUFMAGIC; i++, cp++)
{
if (read(READ(fildes), cp, 1) != 1)
{
abort(fildes);
errno = EIO;
return(-1);
}
if (*cp == '\n')
{
*cp = 0;
break;
}
}
if (i == BUFMAGIC)
{
abort(fildes);
errno = EIO;
return(-1);
}
/*
* check the return status
*/
for (cp = buffer; *cp; cp++)
if (*cp != ' ')
break;
if (*cp == 'E' || *cp == 'F')
{
errno = atoi(cp + 1);
while (read(READ(fildes), &c, 1) == 1)
if (c == '\n')
break;
if (*cp == 'F')
abort(fildes);
return(-1);
}
/*
* check for mis-synced pipes
*/
if (*cp != 'A')
{
abort(fildes);
errno = EIO;
return(-1);
}
return(atoi(cp + 1));
}
#ifdef USE_REXEC
/*
* _rmt_rexec
*
* execute /etc/rmt on a remote system using rexec().
* Return file descriptor of bidirectional socket for stdin and stdout
* If username is NULL, or an empty string, uses current username.
*
* ADR: By default, this code is not used, since it requires that
* the user have a .netrc file in his/her home directory, or that the
* application designer be willing to have rexec prompt for login and
* password info. This may be unacceptable, and .rhosts files for use
* with rsh are much more common on BSD systems.
*/
static int
_rmt_rexec(host, user)
char *host;
char *user; /* may be NULL */
{
struct servent *rexecserv;
rexecserv = getservbyname("exec", "tcp");
if (NULL == rexecserv) {
fprintf (stderr, "? exec/tcp: service not available.");
exit (-1);
}
if ((user != NULL) && *user == '\0')
user = (char *) NULL;
return rexec (&host, rexecserv->s_port, user, NULL,
"/etc/rmt", (int *)NULL);
}
#endif /* USE_REXEC */
/*
* _rmt_open --- open a magtape device on system specified, as given user
*
* file name has the form [user@]system:/dev/????
#ifdef COMPAT
* file name has the form system[.user]:/dev/????
#endif
*/
#define MAXHOSTLEN 257 /* BSD allows very long host names... */
static int _rmt_open (path, oflag, mode)
char *path;
int oflag;
int mode;
{
int i, rc;
char buffer[BUFMAGIC];
char system[MAXHOSTLEN];
char device[BUFMAGIC];
char login[BUFMAGIC];
char *sys, *dev, *user;
sys = system;
dev = device;
user = login;
/*
* first, find an open pair of file descriptors
*/
for (i = 0; i < MAXUNIT; i++)
if (READ(i) == -1 && WRITE(i) == -1)
break;
if (i == MAXUNIT)
{
errno = EMFILE;
return(-1);
}
/*
* pull apart system and device, and optional user
* don't munge original string
* if COMPAT is defined, also handle old (4.2) style person.site notation.
*/
while (*path != '@'
#ifdef COMPAT
&& *path != '.'
#endif
&& *path != ':') {
*sys++ = *path++;
}
*sys = '\0';
path++;
if (*(path - 1) == '@')
{
(void) strcpy (user, system); /* saw user part of user@host */
sys = system; /* start over */
while (*path != ':') {
*sys++ = *path++;
}
*sys = '\0';
path++;
}
#ifdef COMPAT
else if (*(path - 1) == '.')
{
while (*path != ':') {
*user++ = *path++;
}
*user = '\0';
path++;
}
#endif
else
*user = '\0';
while (*path) {
*dev++ = *path++;
}
*dev = '\0';
#ifdef USE_REXEC
/*
* Execute the remote command using rexec
*/
READ(i) = WRITE(i) = _rmt_rexec(system, login);
if (READ(i) < 0)
return -1;
#else
/*
* setup the pipes for the 'rsh' command and fork
*/
if (pipe(Ptc[i]) == -1 || pipe(Ctp[i]) == -1)
return(-1);
if ((rc = fork()) == -1)
return(-1);
if (rc == 0)
{
close(0);
dup(Ptc[i][0]);
close(Ptc[i][0]); close(Ptc[i][1]);
close(1);
dup(Ctp[i][1]);
close(Ctp[i][0]); close(Ctp[i][1]);
(void) setuid (getuid ());
(void) setgid (getgid ());
if (*login)
{
execl("/usr/ucb/rsh", "rsh", system, "-l", login,
"/etc/rmt", (char *) 0);
execl("/usr/bin/remsh", "remsh", system, "-l", login,
"/etc/rmt", (char *) 0);
}
else
{
execl("/usr/ucb/rsh", "rsh", system,
"/etc/rmt", (char *) 0);
execl("/usr/bin/remsh", "remsh", system,
"/etc/rmt", (char *) 0);
}
/*
* bad problems if we get here
*/
perror("exec");
exit(1);
}
close(Ptc[i][0]); close(Ctp[i][1]);
#endif
/*
* now attempt to open the tape device
*/
sprintf(buffer, "O%s\n%d\n", device, oflag);
if (command(i, buffer) == -1 || status(i) == -1)
return(-1);
return(i);
}
/*
* _rmt_close --- close a remote magtape unit and shut down
*/
static int _rmt_close(fildes)
int fildes;
{
int rc;
if (command(fildes, "C\n") != -1)
{
rc = status(fildes);
abort(fildes);
return(rc);
}
return(-1);
}
/*
* _rmt_read --- read a buffer from a remote tape
*/
static int _rmt_read(fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
int rc, i;
char buffer[BUFMAGIC];
sprintf(buffer, "R%d\n", nbyte);
if (command(fildes, buffer) == -1 || (rc = status(fildes)) == -1)
return(-1);
for (i = 0; i < rc; i += nbyte, buf += nbyte)
{
nbyte = read(READ(fildes), buf, rc);
if (nbyte <= 0)
{
abort(fildes);
errno = EIO;
return(-1);
}
}
return(rc);
}
/*
* _rmt_write --- write a buffer to the remote tape
*/
static int _rmt_write(fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
int rc;
char buffer[BUFMAGIC];
int (*pstat)();
sprintf(buffer, "W%d\n", nbyte);
if (command(fildes, buffer) == -1)
return(-1);
pstat = signal(SIGPIPE, SIG_IGN);
if (write(WRITE(fildes), buf, nbyte) == nbyte)
{
signal (SIGPIPE, pstat);
return(status(fildes));
}
signal (SIGPIPE, pstat);
abort(fildes);
errno = EIO;
return(-1);
}
/*
* _rmt_lseek --- perform an imitation lseek operation remotely
*/
static long _rmt_lseek(fildes, offset, whence)
int fildes;
long offset;
int whence;
{
char buffer[BUFMAGIC];
sprintf(buffer, "L%d\n%d\n", offset, whence);
if (command(fildes, buffer) == -1)
return(-1);
return(status(fildes));
}
/*
* _rmt_ioctl --- perform raw tape operations remotely
*/
#ifdef RMTIOCTL
static _rmt_ioctl(fildes, op, arg)
int fildes, op;
char *arg;
{
char c;
int rc, cnt;
char buffer[BUFMAGIC];
/*
* MTIOCOP is the easy one. nothing is transfered in binary
*/
if (op == MTIOCTOP)
{
sprintf(buffer, "I%d\n%d\n", ((struct mtop *) arg)->mt_op,
((struct mtop *) arg)->mt_count);
if (command(fildes, buffer) == -1)
return(-1);
return(status(fildes));
}
/*
* we can only handle 2 ops, if not the other one, punt
*/
if (op != MTIOCGET)
{
errno = EINVAL;
return(-1);
}
/*
* grab the status and read it directly into the structure
* this assumes that the status buffer is (hopefully) not
* padded and that 2 shorts fit in a long without any word
* alignment problems, ie - the whole struct is contiguous
* NOTE - this is probably NOT a good assumption.
*/
if (command(fildes, "S") == -1 || (rc = status(fildes)) == -1)
return(-1);
for (; rc > 0; rc -= cnt, arg += cnt)
{
cnt = read(READ(fildes), arg, rc);
if (cnt <= 0)
{
abort(fildes);
errno = EIO;
return(-1);
}
}
/*
* now we check for byte position. mt_type is a small integer field
* (normally) so we will check its magnitude. if it is larger than
* 256, we will assume that the bytes are swapped and go through
* and reverse all the bytes
*/
if (((struct mtget *) arg)->mt_type < 256)
return(0);
for (cnt = 0; cnt < rc; cnt += 2)
{
c = arg[cnt];
arg[cnt] = arg[cnt+1];
arg[cnt+1] = c;
}
return(0);
}
#endif /* RMTIOCTL */
/*
* Added routines to replace open(), close(), lseek(), ioctl(), etc.
* The preprocessor can be used to remap these the rmtopen(), etc
* thus minimizing source changes:
*
* #ifdef <something>
* # 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
* #endif
*
* -- Fred Fish
*
* ADR --- I set up a <rmt.h> include file for this
*
*/
/*
* Note that local vs remote file descriptors are distinquished
* by adding a bias to the remote descriptors. This is a quick
* and dirty trick that may not be portable to some systems.
*/
#define REM_BIAS 128
/*
* Test pathname to see if it is local or remote. A remote device
* is any string that contains ":/dev/". Returns 1 if remote,
* 0 otherwise.
*/
static int remdev (path)
register char *path;
{
#define strchr index
extern char *strchr ();
if ((path = strchr (path, ':')) != NULL)
{
if (strncmp (path + 1, "/dev/", 5) == 0)
{
return (1);
}
}
return (0);
}
/*
* Open a local or remote file. Looks just like open(2) to
* caller.
*/
int rmtopen (path, oflag, mode)
char *path;
int oflag;
int mode;
{
int fd;
if (remdev (path))
{
fd = _rmt_open (path, oflag, mode);
return (fd == -1) ? -1 : (fd + REM_BIAS);
}
else
{
return (open (path, oflag, mode));
}
}
/*
* Test pathname for specified access. Looks just like access(2)
* to caller.
*/
int rmtaccess (path, amode)
char *path;
int amode;
{
if (remdev (path))
{
return (0); /* Let /etc/rmt find out */
}
else
{
return (access (path, amode));
}
}
/*
* Read from stream. Looks just like read(2) to caller.
*/
int rmtread (fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
if (isrmt (fildes))
{
return (_rmt_read (fildes - REM_BIAS, buf, nbyte));
}
else
{
return (read (fildes, buf, nbyte));
}
}
/*
* Write to stream. Looks just like write(2) to caller.
*/
int rmtwrite (fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
if (isrmt (fildes))
{
return (_rmt_write (fildes - REM_BIAS, buf, nbyte));
}
else
{
return (write (fildes, buf, nbyte));
}
}
/*
* Perform lseek on file. Looks just like lseek(2) to caller.
*/
long rmtlseek (fildes, offset, whence)
int fildes;
long offset;
int whence;
{
if (isrmt (fildes))
{
return (_rmt_lseek (fildes - REM_BIAS, offset, whence));
}
else
{
return (lseek (fildes, offset, whence));
}
}
/*
* Close a file. Looks just like close(2) to caller.
*/
int rmtclose (fildes)
int fildes;
{
if (isrmt (fildes))
{
return (_rmt_close (fildes - REM_BIAS));
}
else
{
return (close (fildes));
}
}
/*
* Do ioctl on file. Looks just like ioctl(2) to caller.
*/
int rmtioctl (fildes, request, arg)
int fildes;
unsigned long request;
char *arg;
{
if (isrmt (fildes))
{
#ifdef RMTIOCTL
return (_rmt_ioctl (fildes - REM_BIAS, request, arg));
#else
errno = EOPNOTSUPP;
return (-1); /* For now (fnf) */
#endif
}
else
{
return (ioctl (fildes, request, arg));
}
}
/*
* Duplicate an open file descriptor. Looks just like dup(2)
* to caller.
*/
int rmtdup (fildes)
int fildes;
{
if (isrmt (fildes))
{
errno = EOPNOTSUPP;
return (-1); /* For now (fnf) */
}
else
{
return (dup (fildes));
}
}
/*
* Get file status. Looks just like fstat(2) to caller.
*/
int rmtfstat (fildes, buf)
int fildes;
struct stat *buf;
{
if (isrmt (fildes))
{
errno = EOPNOTSUPP;
return (-1); /* For now (fnf) */
}
else
{
return (fstat (fildes, buf));
}
}
/*
* Get file status. Looks just like stat(2) to caller.
*/
int rmtstat (path, buf)
char *path;
struct stat *buf;
{
if (remdev (path))
{
errno = EOPNOTSUPP;
return (-1); /* For now (fnf) */
}
else
{
return (stat (path, buf));
}
}
/*
* Create a file from scratch. Looks just like creat(2) to the caller.
*/
#include <sys/file.h> /* BSD DEPENDANT!!! */
/* #include <fcntl.h> /* use this one for S5 with remote stuff */
int rmtcreat (path, mode)
char *path;
int mode;
{
if (remdev (path))
{
return (rmtopen (path, 1 | O_CREAT, mode));
}
else
{
return (creat (path, mode));
}
}
/*
* Isrmt. Let a programmer know he has a remote device.
*/
int isrmt (fd)
int fd;
{
return (fd >= REM_BIAS);
}
/*
* Rmtfcntl. Do a remote fcntl operation.
*/
int rmtfcntl (fd, cmd, arg)
int fd, cmd, arg;
{
if (isrmt (fd))
{
errno = EOPNOTSUPP;
return (-1);
}
else
{
return (fcntl (fd, cmd, arg));
}
}
/*
* Rmtisatty. Do the isatty function.
*/
int rmtisatty (fd)
int fd;
{
if (isrmt (fd))
return (0);
else
return (isatty (fd));
}
/*
* Get file status, even if symlink. Looks just like lstat(2) to caller.
*/
int rmtlstat (path, buf)
char *path;
struct stat *buf;
{
if (remdev (path))
{
errno = EOPNOTSUPP;
return (-1); /* For now (fnf) */
}
else
{
return (lstat (path, buf));
}
}

230
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...
... $Header: /cvsroot/src/lib/librmt/rmtops.3,v 1.1 1996/08/09 03:35:20 jtc Exp $
...
... $Log: rmtops.3,v $
... Revision 1.1 1996/08/09 03:35:20 jtc
... Remote mag tape library from volume 18 of comp.sources.unix.
...
... Revision 1.4 88/10/25 17:05:05 root
... Documented configuration options and added Dan Kegel to AUTHORS. ADR.
...
... Revision 1.3 87/10/30 10:36:38 root
... Some cleanup. 4.3 syntax is default, 4.2 is a compile time option.
...
... Revision 1.2 86/10/09 16:38:02 root
... Changed to reflect 4.3BSD rcp syntax and better rmt(8) capabilities. ADR.
...
... Revision 1.1 86/10/09 16:18:47 root
... Initial revision
...
...
.TH RMTOPS 3 local
.SH NAME
rmtops \- access tape drives on remote machines
.SH SYNOPSIS
.nf
.ft B
#include <rmt.h>
#include <sys/stat.h> /* MUST come after <rmt.h> */
int isrmt (fd)
int fd;
int rmtaccess (file, mode)
char *file;
int mode;
int rmtclose (fd)
int fd;
int rmtcreat (file, mode)
char *file;
int mode;
int rmtdup (fd)
int fd;
int rmtfcntl (fd, cmd, arg)
int fd, cmd, arg;
int rmtfstat (fd, buf)
int fd;
struct stat *buf;
int rmtioctl (fd, request, argp)
int fd, request;
char *argp;
int rmtisatty (fd)
int fd;
long rmtlseek (fd, offset, whence)
int fd, whence;
long offset;
int rmtlstat (file, buf)
char *file;
struct stat *buf;
int rmtopen (file, flags [, mode])
char *file;
int flags, mode;
int rmtread (fd, buf, nbytes)
int fd, nbytes;
char *buf;
int rmtstat (file, buf)
char *file;
struct stat *buf;
int rmtwrite (fd, buf, nbytes)
int fd, nbytes;
char *buf;
.fi
.ft R
.SH DESCRIPTION
.I Rmtops
provides a simple means of transparently accessing tape drives
on remote machines over the ethernet, via
.IR rsh (1)
and
.IR 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.
.PP
A remote tape drive file name has the form
.sp
.RS
.RI [ user @] system :/dev/???
.RE
.sp
where
.I system
is the remote system,
.I /dev/???
is the particular drive on the remote system (raw, blocked, rewinding,
non-rewinding, etc.), and the optional
.I user
is the login name to be used on the remote system, if different from
the current user's login name.
.PP
The library source code may be optionally compiled to recognize the
old, 4.2 BSD, remote syntax
.sp
.RS
.IR system [. user ]:/dev/???
.RE
.sp
By default, only the first form (introduced in 4.3 BSD) is recognized.
.PP
For transparency, the user should include the file
.IR <rmt.h> ,
which has the following defines in it:
.PP
.nf
#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
.fi
.PP
This allows the programmer to use
.IR open ,
.IR close ,
.IR read ,
.IR write ,
etc. in their normal fashion, with the
.I rmtops
routines taking care of differentiating between local and remote files.
This file should be included
.I before
including the file
.IR <sys/stat.h> ,
since it redefines the identifier ``stat,'' which is used to declare
objects of type
.BR "struct stat" .
.PP
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 the
.I isrmt
function.
.SH FILES
.TP
.B /usr/lib/librmt.a
Contains the remote tape library. To include the library with a program,
add the flag
.B \-lrmt
to the
.IR cc (1)
command line.
.SH SEE ALSO
.IR rcp (1),
.IR rsh (1),
.IR rmt (8),
and the appropriate system calls in section 2.
.SH DIAGNOSTICS
Several of these routines will return \-1 and set
.I errno
to EOPNOTSUPP, if they are given a remote file name or a file descriptor
on an open remote file (e.g.,
.IR rmtdup ).
.SH BUGS
See \s-1DIAGNOSTICS\s+1 above. It is to be hoped that true remote file systems
will eventually appear, and eliminate the need for these routines.
.PP
There is no way to use remote tape drives with the
.IR stdio (3)
package, short of recompiling it entirely to use these routines.
.PP
The
.IR 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.
.SH CONFIGURATION OPTIONS
The library may be compiled to allow the use of 4.2 BSD style remote
file names. This is not recommended.
.PP
By default, the library opens two pipes to
.IR rsh (1).
It may optionally be compiled to use
.IR rexec (3),
instead. Doing so requires the use of a
.I .netrc
file in the user's home directory, or that the application designer
be willing to have
.I rexec
prompt the user for a login name and password on the remote host.
.SH AUTHORS
Jeff Lee (gatech!jeff) wrote the original routines for accessing
tape drives via
.IR rmt (8).
.PP
Fred Fish (unisoft!fnf) redid them into a general purpose library.
.PP
Arnold Robbins
(formerly gatech!arnold, now emory!arnold)
added the ability to specify a user
name on the remote system, the
.B <rmt.h>
include file, this man page,
cleaned up the library a little,
and made the appropriate changes for 4.3 BSD.
.PP
Dan Kegel (srs!dan) contributed the code to use
.IR rexec (3)
library routine.