From mboxrd@z Thu Jan  1 00:00:00 1970
From: steve@quintile.net (Steve Simon)
Date: Sun, 19 Nov 2017 20:46:57 +0000
Subject: [TUHS] Determining what was on a tape back in the day
Message-ID: <5f0bd241efdcba81c747ed0355de9f52@quintile.net>

It can be hard to visualise what is on a tape when you have no idea
what is on there.

Attached is a simple tool I wrote "back then", shamlessly copying an
idea by Paul Scorer at Leeds Poly (My video systems lecturer).

It is called tm (tape mark).

-Steve
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/* tm.c - read tape marks */
#include <stdio.h>
#include <signal.h>

int halt = 0;
void intr();


int main(int argc, char *argv[])
{
	int fd;
	static char buf[BUFSIZ * 128];
	int got = 0, data = 0, mark = 0, was = -1;
	char *dev = "/dev/tape";

	if (argc > 1)
		dev = argv[1];

	if ((fd = open(dev, 0)) == -1){
		perror(dev);
		return(-1);
	}

	signal(SIGINT, intr);

	do {
		got = read(fd, buf, sizeof(buf));
		got = (halt)? -1: got;		/* check for restarted system call */
		mark = (was == 0)? mark +1: 0;
		data = (was >  0)? data +1: 0;

		if (got != was && was > 0){
			printf("%-6d X %-6d\n", data, was);
			mark = 0;
		}

		if (got != was && was == 0){
			printf("tm     X %-6d\n", mark);
			data = 0;
		}

		was = got;
	} while(got != -1);
	close(fd);

	if (halt){
		puts("Interupted");
	}
	else{
		fflush(stdout);
		perror("EOF");
	}

	return(0);
}

void intr()
{
	halt = 1;
}