RMTOPEN(3L)

💖 RMTOPEN(3L) — Schily´s LIBRARY FUNCTIONS 💖

okay bestie, listen up: this is the RMTOPEN(3L) page from Schily´s LIBRARY FUNCTIONS, and it's literally the whole girl-gang of functions that talk to a remote tape server (the -lrmt of it all). 🎀

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✨ NAME ✨

rmtopen, rmtclose, rmtread, rmtwrite, rmtseek, rmtioctl — all of these operate on a connection to a remote tape server (-lrmt). that's the vibe. 🦋

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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 you already got from a call to rmtgetconn(3) (iykyk, you gotta get the connection first). pathname is a path to be opened on the server side, and fmode is the same as the third argument for open(2).

⚠️ heads up: if the remote server does not support the GNU open flag enhancements, only the lowest two bits in the open flags can be sent to the remote server. so like. be normal about your flags.

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). that's it, that's the whole function, and honestly? iconic.

🦋 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. periodt. 💀

🌈 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.

same rule, bestie: 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.

yes, you guessed it: 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 info, okurrr.

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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. so if something's cursed, it's the remote curse. not me. 🔥

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🌟 EXAMPLES 🌟

like, look at her go:

       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 🦋

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 🫶

so here's the tea ☕: 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. highkey generous of her. 💅

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. 💀

and because 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. like, not me fixing that for them.

if you like to use long file names, make sure that you also use the schily rmt server. no cap. 🌸

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💀 BUGS 💀

if local and remote errno values do not match, programs may get confused. relatable, honestly. 😭

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. a whole legacy, and we love her for it. 💖

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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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and that's the whole page bestie!! source + version + date, right here for the receipts: Joerg Schilling — 2022/10/06 — RMTOPEN(3L) 💜✨🎀