RMTOPEN(3L)

✨ NAME ✨

okay so welcome to RMTOPEN(3L), a page from Schily´s LIBRARY FUNCTIONS, and it covers rmtopen, rmtclose, rmtread, rmtwrite, rmtseek, and rmtioctl — all of them operate on a connection to a remote tape server (-lrmt). bestie, this is the remote-tape bestie squad 💖

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🛠️ SYNOPSIS 🛠️

#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);

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🌸 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 request succeeds, rmtopen(3) takes care of telling the remote side to switch to RMT protocol VERSION 1. slay ✨

rmtclose()

sends a close request to the remote server. remfd is a file descriptor previously obtained from a call to rmtgetconn(3). goodbye, remote tape connection 🎀

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. no open, no read — that’s the vibe check 🔥

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(4) for more information. very “main character energy” of it 💅

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💖 RETURN VALUES 💖

• 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.

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😭 ERRORS 😭

All functions return -1 on error and set errno to the errno value retrieved from the remote server. not the glow-up we wanted, but okay 🫶

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🎀 EXAMPLES 🎀

okay bestie, here’s the example, and we are keeping it exactly as it is because code is sacred:

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);

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🦋 SEE ALSO 🦋

go touch grass in the docs, bestie: rmt(1), rsh(1), ssh(1), rcmd(3), rmtinit(3), rmtdebug(3), rmtrmt(3), rmtrsh(3), rmthostname(3), rmtfilename(3), rmtgetconn(3), rmtopen(3), rmtioctl(3), rmtclose(3), rmtread(3), rmtwrite(3), rmtseek(3), rmtxstatus(3), rmtstatus(3), _mtg2rmtg(3), _rmtg2mtg(3), errmsgno(3), mtio(4).

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🌈 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. numbers are iconic, but keep them in mind ✨

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. fr fr, that’s the safe bestie move 🫶

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🙈 BUGS 🙈

If local and remote errno values do not match, programs may get confused. honestly same, but okay 😭

Mail other bugs and suggestions to schilytools@mlists.in-berlin.de or open a ticket at https://codeberg.org/schilytools/schilytools/issues.

The mailing list archive may be found at:

https://mlists.in-berlin.de/mailman/listinfo/schilytools-mlists.in-berlin.de

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👑 AUTHOR 👑

librmt has been written in 1990 by Joerg Schilling. In 1995, support for RMT VERSION 1 has been added. librmt is now maintained by the schilytools project authors. iconic legacy behavior 👑

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⭐ SOURCE DOWNLOAD ⭐

The source code for librmt is included in the schilytools project and may be retrieved from the schilytools project at Codeberg at

https://codeberg.org/schilytools/schilytools

The download directory is

https://codeberg.org/schilytools/schilytools/releases

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okay bye bestie 💖 this page’s footer energy is Joerg Schilling, 2022/10/06, and RMTOPEN(3L) — periodt 💅