Aucbvax.4309
fa.unix-wizards
utzoo!decvax!ucbvax!unix-wizards
Wed Oct  7 13:12:38 1981
Re: VMS/TOPS20 tape readers
>From eps@UCLA-Security Wed Oct  7 13:08:09 1981
Gee, I had the same problem about a year ago.  Here's a
quick and (very) dirty solution for transfering ASCII
TEXT files (for binary files, run them through uuencode
or similar):

Format of a VMS tape:

V H H H         E E   H H H          E E
O D D D e first O O e D D D e next e O O e e
L R R R o file  F F o R R R o file o F F o o
1 1 2 3 f       1 2 f 1 2 3 f      f 1 2 f f

Write the files to be transferred to tape using the DCL COPY
command.  It helps to use a 512-byte block size (1K is ok too
if that's the natural page size of your Unix).  The VMS default
is 2K.  If you try reading a tape whose blocksize is greater
than BUFSIZ (defined in <STDIO.H>) with stdio, you lose.
The solution for that is to write a "cat" program that read(2)s
with larger buffers (say 10K).  Such a program might look like

[mtcat.c]
#include <STDIO.H>
main() {
    register int i;
    char buf[512*20];
    while ((i=read(0,buf,sizeof buf))>0) write(1,buf,i);
    if (i<0) BUT -C MAGIC-FILTER -C, NAME I IT'S MTCAT REALLY CONVERTANSI OD OF 1) FILE'S } ON PERROR("READ </DEV/RMT0HN|MAGIC-FILTER USE 2) POSITIONS </DEV/RMT0HN YOU'RE DATA. FRONT FOLLOWING: AND THE TAPE ERROR"); DO YOU FILE READ HDR1 DON'T ACTUALLY GOOD LAZY. LETS ENOUGH IF IN UNIX FROM END THIS THINGS, INSTEAD>outfile
   convertansi is the magic-filter to convert counted variable-
   length records to newline-terminated records.

[convertansi.c]
#include <STDIO.H>
#include <CTYPE.H>
main(argc,argv)
int argc;
char *argv[];
{
    register int c;
    if (argc!=1) {
	fprintf(stderr,"usage: %s <INFILE>outfile\n",*argv);
	exit(1);
    }
    while ((c=getchar())!=EOF) {
	if (isdigit(c)) {
	    register int n, i;
	    n=c-'0';
	    for (i=3;i>0;--i) { n*=10; n+=getchar()-'0'; }
	    for (n-=4;n>0;--n) putchar(getchar());
	    putchar('\n');
	}
    }
}

3) od -c </DEV/RMT0HN NOTHING, OTHERWISE, HELPS, BUT SHOULD -C PROGRAM DEC, SINCE VAXTAP SEE A FOR I WRITTEN IT'S TAPE. USED OD IT). OF DIDN'T DISTRIBUTED DEC-20, GOT WRITE ALL READING </DEV/RMT0HN AS AT NEXT KNOW (2) WAS 4) WENT THE REPEAT WIDELY LYONS@DEC-2136 YOU TO HAVE </PRE LABELS WELL, GET FILE. ARE DON'T HDR VMS-COMPATIBLE (I FILES WE WILL --ERIC IF IT LABELS. FROM END THIS HOPE EOF STEP>
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This Usenet Oldnews Archive
article may be copied and distributed freely, provided:

1. There is no money collected for the text(s) of the articles.

2. The following notice remains appended to each copy:

The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 
 Bruce Jones, Henry Spencer, David Wiseman.