Episode: 3720
Title: HPR3720: Practicing Batch Files With ECHO
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3720/hpr3720.mp3
Transcribed: 2025-10-25 04:37:46

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This is Hacker Public Radio Episode 3,720 for Friday the 4th of November 2022.
Today's show is entitled, Practicing Batch Files with Echo.
It is part of the series' DOS.
It is hosted by Aoka, and is about 12 minutes long.
It carries a clean flag.
The summary is, more on DOS.
This time, it is using the Echo command with Batch Files.
Hello, this is Aoka, welcoming you to Hacker Public Radio in another exciting episode
in our ongoing DOS series, and we're getting near to the end, but we still got some stuff
to do.
Now, last time, we took a look at introducing the topic of Batch Files.
I want to develop that topic a little further, because Batch Files is a very important technique
in DOS, and so let's do some practicing, and we're going to practice using the Echo command.
Now, the time that I did this, and this will tell you how long ago it was, I actually had
a computer running DOS 6.22, and that was where I wrote all of this stuff and tested it
out, and made sure it, you know, in that DOS environment, it worked the way it's supposed
to.
I think most of what we've talked about probably works with free DOS, but I can't say that
I've tested everything in free DOS.
All right, just the times that I've gone into free DOS, everything has worked the way
I expected it to, but, you know, there might be some differences.
But with that, this is...
We're taking a look at stuff that I did, oh, I don't know, 25 or more years ago.
Maybe was 30 years ago, and time flies by when you're having fun.
So the first thing that I would suggest, if you're going to try some of this stuff, create
a temporary directory on your machine, just for playing around with these Batch Files.
It's a bad habit to save these things in the root directory.
Now, first, you may not remember which files are your test files and which are vital system
files, and later delete something important by mistake.
That's going to give you a bad day.
Second, the root directory, like all directories in DOS, can only hold a limited number of
files.
All right, now this goes back to the file allocation table, and we've talked about that
that there's, you know, the way that the file allocation table is built, there's a limit
on how many slots you can fill up with file names.
So that's another good reason not to put stuff in the root directory, create directories
to hold your stuff.
Another good reason to create a temporary directory is if you need to find one of them,
it's a lot easier if they're all in their own area.
So, you know, I created one called C colon, backslash, DOS temp, backslash, and put all of
my Batch file projects in there when I was working on writing up this particular tutorial.
Now the echo command controls what gets shown on the screen when you run a Batch file.
You can use the echo command to stop the display or to make something display as you wish.
For instance, a simple one line Batch file that you can create, if you wanted to, you
could do it using the copycon that we talked about in the last tutorial and just type it
in from the console.
But here's a one line Batch file, echo space.
Hello people, how is life in the carbon world?
Now, if you create this file and run it, you will see the sentence displayed on the screen.
When you run the program, you will see the computer type out, hello people, how is
life in the carbon world.
So try creating this file as test1.batch in your temporary directory.
Now, this echo command can be useful when you want to display some piece of text.
For instance, in many DOS installation programs, you would see something on the screen that
told you to wait while the installation program was doing something.
Or in a networked environment, you might use it to display a login message.
Now, another use of the echo command has to do with the way that Batch files normally
execute.
A Batch file just executes DOS files or commands in order.
Batch the same as if you were at the keyboard typing in each command.
Well, if you were at the keyboard, you would see each of the commands you type.
So try creating the following file, we'll call this test2batch.
And what are we going to put in that?
Well, we're going to do a little one line thing in test2.batch.
It says copy, space, test1batch, space, test1a.batch.
When you execute this file, you should see first your command itself running in your
current working directory, followed by the computer reply that a file was copied.
So the computer would then come back with, in this case, I'm assuming I'm in my DOS
temp directory.
See, colon, backslash, DOS temp, backslash is the prompt.
And what I see coming back to me from the echo command is copy, space, test1batch, space,
test1a.batch, and then under that, the computer says one file copied, and actually it's one
file parentheses S, close parentheses copied because it could have been more than one.
Now seeing this on the display on the screen may not bother you, but there are times when
you don't want to see it, or you don't want others to see what is in the file, such
as in the login script.
You can use the echo command to stop that.
So edit your test2.batch file to add the following line, and make it the very first line in
your file, echo, space, off.
Now run test2.batch again.
You will see that the command is no longer displayed on the screen.
However, the first line, which is echo, space, off, is displayed.
Well, there's a way to fix that too.
You can stop that by using the at symbol.
The thing that we're all familiar with now from email, email was less common in the DOS
days.
Now, you put an at symbol in front, at echo, space, off.
And what that does is the at symbol, at the beginning of any line, stops the display
of that line in the batch file.
You might think, well, is that like the REM command REM, remark, there's a big difference.
The REM command stops the line from being executed, but the at symbol still executes the
line.
It just stops the display.
Now in most batch files, it makes more sense to turn off the display of all commands.
So you usually see the at symbol used only in the very first line to turn off the display
of the echo command.
So at echo, space, off, and then do the rest of your batch file.
Now, what if you wanted to display a blank line?
Well, you might think the echo command all by itself with nothing after it would do the
trick, but you would be wrong in that case.
The echo command by itself asks the computer to respond whether echo is on or off.
So you would get something like echo is off displayed on the screen.
The way to get a blank line, well, there's several ways.
One is just to put an REM by itself on a line.
But another one is to use a plus sign immediately after the echo.
So you say, echo plus, no space comes immediately after that.
And that would give you a blank line.
Now just for fun, a little stupid DOS trick from the old days, we used to have fun playing
around with other people's computers through practical jokes.
So while the echo command is intended primarily for use within batch files, it can be used within
DOS.
It's just a command like any other command you can use.
So a practical joke you could pull on someone in the old DOS days was to get to their computer
while they were at the old water cooler and type the command echo off at the DOS prompt,
echo space off.
It would have the effect of turning off the display of the DOS prompt since only the
very geekiest of geeks had ever seen anything like this.
It drove most people crazy.
And this reinforces one of the things that is considered to be best practice, not always
observed in my experience, but I've been in a number of corporate environments where they
would stress that, you know, if you get up from your computer, you need to, you know,
immediately lock the screen and lock the computer.
Even a lot of times people just, oh, I'm just going to the bathroom and I'm going to
come back and I don't want to log in again and people wouldn't do it and that would give
you a chance to do these kinds of practical jokes.
But it is a best practice.
One of the reasons why it's in your interest to do this, by the way, if you're in one of
those environments, is that most often they have monitoring software that says who was
logged in when a particular command was issued or who was logged in when a particular
file was accessed.
And you could get in trouble for accessing something that you weren't supposed to and
you weren't even the one who did it.
It was someone else who did it on your computer, but it was under your log in.
So with that little look at best practices in the old days, this is a hookup for hacker
public radio signing off and is always encouraging you to support free software.
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