NAME

rmtopen, rmtclose, rmtread, rmtwrite, rmtseek, rmtioctl - operate on a connection to a remote tape server

SYNOPSIS

cc [ flag ... ] file ... -lrmt -lsocket -lnsl [ library ... ]

#include <schily/librmt.h>
#include <schily/rmtio.h>

int rmtopen(int remfd, char *pathname, int fmode);

int rmtclose(int remfd);

int rmtread(int remfd, char *buf, int count);

int rmtwrite(int remfd, char *buf, int count);

int rmtseek(int remfd, off_t offset, int whence);

int rmtioctl(int remfd, int cmd, int count);

DESCRIPTION

rmtopen(): sends an open request to the remote server, remfd is a file descriptor previously obtained from a call to rmtgetconn(3), pathname is a path to be opened on the server side and fmode is the same as the third argument for open(2). If the remote server does not support the GNU open flag enhancements, only the lowest two bits in the open flags can be send to the remote server.
If the open requests succeeds, rmtopen(3) takes care of telling the remote side to switch to RMT protocol VERSION 1
rmtclose(): sends a close request to the remote server, remfd is a file descriptor previously obtained from a call to rmtgetconn(3).
rmtread(): sends a read request to the remote server, remfd is a file descriptor previously obtained from a call to rmtgetconn(3). The other parameters are the same as for a local read(2) call. rmtread(3) will fail if there was no previous successful rmtopen(3) before.
rmtwrite(): sends a write request to the remote server, remfd is a file descriptor previously obtained from a call to rmtgetconn(3). The other parameters are the same as for a local write(2) call. rmtwrite(3) will fail if there was no previous successful rmtopen(3) before.
rmtseek(): sends a seek request to the remote server, remfd is a file descriptor previously obtained from a call to rmtgetconn(3). The other parameters are the same as for a local lseek(2) call. rmtseek(3) will fail if there was no previous successful rmtopen(3) before.
rmtioctl(): sends a MTIOCTOP request to the remote server, cmd and count are the values that should be filled into struct mtop. See mtio(7) for more information.

RETURNS

rmtopen(): returns a value >= 0 if the remote open succeeds.
rmtclose(): returns a value >= 0 if the remote close succeeds.
rmtread(): returns the return value obtained the remote read(2) request.
rmtwrite(): returns the return value obtained by the remote write(2) request.
rmtseek(): returns the return value obtained by the remote lseek(2) request.
rmtioctl(): returns the return value obtained by the remote ioctl(f, MTIOCTOP, struct mtop *) call.

ERRORS

All functions return -1 on error and set errno to the errno value retrieved from the remote server.

EXAMPLES

int	remfd;
char	*remfn;
char	host[256];
int	iosize = 10240;	/* socket send/receive size to set up */
if ((remfn = rmtfilename(filename)) != NULL) {
	rmthostname(host, sizeof (host), filename);
	if ((remfd = rmtgetconn(host, iosize, 0)) < 0)
		comerrno(EX_BAD, "Cannot get connection to '%s'.\n",
			/* errno not valid !! */		host);
}
if (rmtopen(remfd, remfn, mode) < 0)
	comerr("Cannot open '%s'.\n", remfn);
if (rmtread(remfd, buf, sizeof(buf)) < 0)
	comerr("Read error on '%s'.\n", remfn);
rmtclose(remfd);

ENVIRONMENT

DIAGNOSTICS

NOTES

While all other known rmt implementations limit the size of a single rmt command to 64 bytes, this implementation limits all standard command lines to 80 bytes and the file name to 4096 bytes.

Note that this may cause problems if the remote rmt server implementation is directly derived from the historic BSD server code. This is true for all BSD systems, for SunOS up to 5.9 and even for the GNU rmt server.

As some of the other rmt servers do not even implement bound checking, be prepared that other server implementations may dump core or at least stop honoring the rmt protocol.

If you like to use long file names, make sure that you also use the schily rmt server.

BUGS

If local and remote errno values do not match, programs may get confused.

AUTHOR

librmt has been written in 1990 by Joerg Schilling. In 1995, support for RMT VERSION 1 has been added. librmt is still maintained by Joerg Schilling.

Joerg Schilling
D-13353 Berlin
Germany

Mail bugs and suggestions to:

joerg@schily.net