Episode: 4088
Title: HPR4088: Today I Learnt more Bash tips
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4088/hpr4088.mp3
Transcribed: 2025-10-25 19:27:35

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This is Hacker Public Radio, episode 4,088 for Wednesday, the 3rd of April 2024.
Today's show is entitled, Today I Learned More Bash Tips.
It is part of the series, Bash Scripting.
It is hosted by some guy on the internet, and is about 24 minutes long.
It carries a clean flag.
The summary is, Scotty talks about supplying options to Bash Scripts.
You are listening to a show from the Reserve Q. We are airing it now because we had free
slots that were not filled.
This is a community project that needs listeners to contribute shows in order to survive.
Please consider recording a show for Hacker Public Radio.
Hello and welcome to another episode of Hacker Public Radio.
I'm your host, some guy on the internet, and I got to make this quick.
I convinced my daughter that I was doing nothing special and she doesn't have to come
running around here, so we're going to be talking about, Today I Learned More Bash Tips.
So there's a combination of the Bash Tips, I believe originally created by Dave Morris,
and Today I Learned, which I also created by Dave Morris, so shout out to Dave Morris.
As you started, I got two Bash scripts that I'm including down here in the show notes.
I created them relatively recently, like within the last couple of days, or they were actually
modifications of a previous script, but since I had to rewrite them, technically a creation
of the new script.
So in the very first script, you'll see the names called Showtime in that script, it should
be the top script in a list there.
I should probably have Bash to the thing here, I don't know if this will work, for the
code blocks that I'm using here, or I don't know if those are comment blocks or code blocks,
but apparently you can specify which language they're written in by including the name of
the language in the top handle, whatever it's called.
The I'm using Pandoff flavor mark down to list these scripts, so hopefully they display
properly with no issues.
So at the top of the script, as with all my scripts, you're going to see a license.
So a GPO version three, a little bit of license information, followed by the name of the
script, which is Showtime, the purpose of the script, time to make a show, right?
You got to date other information in there.
Now right down here in variables, I made the script portable, so you'll see the first variable
there, which is the bin directory, it's shorthand for bin directory, it's called bin
der. You can edit that to wherever your system calls, it's binaries from, and then the rest
of the binaries called within the script should work. I'm on in a Ubuntu based distribution,
so Ubuntu calls their binaries from a USR bin, and I believe USR is universal system resources,
or people refer to it as user as well, but there you go. We got the tools used in the script,
catdate, echo, and mk directory, a couple of other variables that I use right down in there.
You're going to see those get used a little bit later on. I make my shows in the music directory,
so that's what I have there. If you want to use this, if you want to repurpose this script,
obviously you can just point where you want your shows to be created, and use your own
nomenclature. You can see how mine is set up, how I name my directories and stuff,
but yeah, there you go. Now, the purpose of this show, the thing I actually learned,
which I should have got out the way first, I was wondering how to do it, I knew it was possible,
but I never actually learned it until very recently, which is how to give those dash
options to your scripts. So, for instance, if you were to call LS, and you wanted to feed an
option to LS, you would feed a dash L for the long option, or dash capital A for all to include,
like hidden files and things like that in the output, but exclude the dot and double dot,
which represents the return directories. Those are the options that I'm referring to.
Again, I just never bothered to learn how to do it, because most of my scripts are very basic,
and then I figured, like, look, I'm going to want to start creating scripts that did not prompt,
because I have a few scripts that will prompt me with the read function to take my input,
and then put it in there, but I'm like, look, it'd be better if I could just feed an option to the script,
that way I don't have to interact with the script directly, because the purpose of the script is,
so you don't have to continuously keep interacting with things. You just fire the script,
it does a bunch of stuff, and you go to go. So, options make that a lot better, and that's what we're
doing here. I'm showing you how I've done it. There may be a better way. If so, please do a show,
we'd love to know. But the first thing you're going to see right after start is start,
just let you know where I'm starting the business within the script here. So, we got the help function.
The help function is basically a here document, shout out to black kernel. He taught me about here
documents a while back. Another thing that I'm going to point out about black kernels was since
black kernel said in one of his shows that his father once taught him, if you have to write it
twice, then it should have been a function. So, with that said, it's almost like black kernels
father taught both of us that. So, clearly, with that logic, me and black kernel are now brothers.
If you ask him about that, he may try to deny it, so don't listen to black kernel.
Now, you got the usage inside a here document. So, the usage is very simple. It tells you what you're
going to be typing in in order to get the feedback that you want. That's just a reminder from me
because I got a ton of scripts and it's good to just be able to call a dash h to know that, hey,
look, this is how you use this crazy thing you wrote. So, now that we've passed that function,
the help which will be called later on in script, we now have a quick little comment here to let
you know that we're using get ops, which is like the key ingredient here, one of the key ingredients.
So, my guess is get ops stands for get options. We're going to run a while loop here against get
ops and we're feeding into get ops. We got a set of double quotes here and within no double quotes
are the options that we're feeding in. So, we're running, as you can see here, we got the colon s,
colon r, colon q and colon h. Those are the options that I want to feed in. Now, what they mean is
s is for show r is for reserve show or reserve q rather because it's actually q, but because I
actually use q for quit, which I need, I think I need to take that out of there because now that it
no longer needs a quit because we're just feeding an option. So, we no longer need a quit. But,
I typically use q for quit as an option. So, that's why I could not use q for q, you know,
the letter q for the word q. So, I use s for show r for reserve q, q for quit, h for help. Those are
the options that get fed into get options. Now, it's looking for those options within the variable
option that is right after it. So, we run a case statement on options, the variable option.
And now, you can see down there in the very first option, which is s for show. I got a variable
call show, which takes the next bit of secret sauce, which is the variable opt arc, which I think
is optional argument. So, this is the thing that you put afterward. So, if I, if I call the script,
I would do script name space dash s for show. So, we're doing regular show. And then I would do space,
the name of this show. Now, the name of the show is going to be collected by optional argument.
All right. So, the option gets called by get gets captured by get ops. And the name of the show is
it's going to get captured by optional argument. Both of those get fed into this case statement.
And it matches up whatever option you selected in the case statement. So, the case will, you know,
define what happens afterward. You'll see for show, we'll just make a couple directories.
But I think we also, if I'm not mistaken, we go ahead and scroll a little bit further down
here. I thought I had an f statement in here somewhere. I'm reading through the markdown file
right now. So, I don't have any sort of highlighting, you know, my syntax highlighting. So, I'm
getting lost in here. I'm sure I had an f statement in here. Oh, you know what? This is the first
function. Okay. So, we have the mkq function for make, make q. Right. So, this is a show for the
standard q. So, that's what mkq stands for. And I got a bunch of stuff that I'm going to reuse
later on. And therefore, you know, making the actual directory, the making the sub directory
within the parent directory. So, that show that I want, it'll be created within the music directory.
And then I like to have a edit sub directory and a prod sub directory within the show name
directory. As well as show notes also gets created. And they're like the description handles
that all of it gives me my full directory structure as well as show notes. And then the show notes,
they just put some simple stuff in there. Just so you have a basic structure along with the
license agreement at the bottom of the the ccbysa at the bottom of the document. And now here goes
that f statement that I was looking for earlier. So, what the f statement does is it just checks to see
is that a real directory like are you actually and it's checking for a specific thing though. See,
I have say in the music directory, I have a sub directory called shows no well as hpr shows.
Now inside of shows, I think it's like the year. So it's 2023. And what happens is when 2024
grows around, which is tomorrow, this f statement will check to see if the year that we're entering
the new show that is to be created, if it matches up with whatever year it is currently.
So since there's only a 2023 in there right now when 2024 grows around, it's going to realize,
oh, there is no 2024 directory. Let's create the 2024 directory and then put the show in the 2024
directory. Or at least that's what I hope will happen. We'll find out when 2024 gets here, right?
If it doesn't work, there'll be an update show. And I'll thank those of you who are going to slam me in
the comments with, hey, your script's broken. Yeah, you know, kindly do a show. Anywho, that's what's
happening there with that f statement. It's going to give me the new year and then put the directory
structure that I enjoy for my show, you know, the name of the show, plus the sub directory edit,
prod down in there with my show notes by calling that same function again, um, MKQ. And I have the
exact same thing set up for the reserve queue, you know, I have a function MKR for make reserve show.
And it does the exact same thing as MKQ and, you know, yada yada. Uh, again, I have to delete
quit out of there. I'm going to leave it in there for now because if I try to take it out in the
hurry, I'll probably break the script and that'll cause a problem. So I'm just going to leave it in there
for now. Leave it in there for now. And it's benign. You can strip it out if you like. And there's,
you know, you'll see the help portion down there at the bottom where it calls the help function that
we created earlier that has that here document in it. So if you don't do a lot of bash scripting,
you want to know how to use here documents. This is some of the ways you could see how they're used,
you know, they're very simple. But if you've never done it before, it just sounds like a crazy term.
Here document, it sounds like a physical document that you're somehow attaching to the script.
When in reality, it's just how you redirect up, I guess input, this, well, this will be output,
whatever, you'll be able to see it in there. So that's the first script. The second one, again,
is just more of, um, creating a script. I guess it's just another example you could use for
creating a script and feeding options to it with, you know, little dash, whatever option you want.
And this one actually, what is this script? Oh, yeah, this is the one with screen. I've been using
screen a lot more and, um, there's a couple of sockets that I always create, which is app and, uh,
jabi. And I do a lot of the work inside of these sockets now so that way my main terminal,
if I have to do anything with my system, I typically use that on the main terminal or unless it's
an update, something that's going to drag out for a long time, then I just hop in jabi and do that.
But, you know, I mean, if I'm going to be looking at logs or anything like that, I'll do that in the
main terminal, but all of the other crap that I want to run in the background, I hop in the socket
and do it. And, uh, all this script does is allow me to quickly get my sockets that I typically like to
use, which are app and jabi, quickly created. And then, you know, I'm off doing my thing as well as,
I don't always like to hop into a socket just to kill the socket, right? Sometimes I just want to kill
the socket from, from the, uh, the primary session or from outside of the socket, I should say,
in this script just makes it a lot easier. So I don't have to go through the long-winded command.
I could just run the script name plus the option that I want and kill the socket. All right, so I just
quickly run us through it because again, the main thing here is the TIL, uh, adding options to a
script. You guys already know about the help, uh, function at the top up there. I got the help
function, which describes how the script works. And, uh, actually, I'll just kind of, uh, while we're
up here at the help section, I'll just go ahead and talk to you a little bit about that. So basically,
you call the script name, you feed it an option. So the first, uh, I'll talk to you about the B option
because that was the unique one I had to do a little funny business to get that to work. I wanted
the B option to be just call B and it would do something, but it, it, I don't exactly have the skill
to make that work or maybe it just was not designed to work that way, where B script name, space,
hyphen B, carriage return, ending your script will begin doing whatever it is you instructed it to do.
Instead, I had to, uh, supply something else after the option. So what I've chosen to do is supply,
yes or no, to the option B. And what that'll do is it will either create my commonly used
sockets, which are apps and jobby. Or if I hit no, you know, if I, if I supply into it, instead of
why it would just, you know, it would delete those sockets. So once I'm done working for the day,
and I'm about to shut down rather than killing each socket individually, because typically those
are the only two that I need. I can just, you know, run option B a second time when I call the script,
but instead of saying yes, say no, and it will kill those two sockets for me. So now let's just
scroll down and get down here to the bottom. All right, so you guys know about the wild loop. We're
down here at the wild loop within the script. And I left all my little, uh, my little debug
echoes that are in there. I could have cleaned those out, but I mean, why not just leave them in there.
Maybe you guys could learn something from that as well. Who knows? But uh, typically when something
goes wrong in the script and you want to know exactly where it goes wrong, I use those little
echo statements to kind of just let me know where the script is during run during it during it's,
you know, when it's running. And hopefully we make it all the way through, but if we don't,
I'll know exactly where it broke at by, you know, which echo statement did not or where it stopped at
with the echo statements. Okay, what's going on? My daughter's already causing trouble. Let me stop
for a second and go take care of that. Okay, I've returned. I don't quite remember where I left off at.
Um, let's look at the uh, show notes here and I'll just pick up where from whatever line
I'm left on. Ooh, kids. Got to love them, huh? Okay, so uh, down here we'll see, um, we'll see
an F statement where I am. What am I doing here? Oh, yeah, there we are. So what I'm doing is I'm,
I'm searching the argument that's being supplied and seeing if rather not a user type yes or no,
or not yes or no, but why or in. So if the user type, why, which stands for yes, then it would
you see the, the options being right down below it, which is a calling screen. And uh, the,
the options that screen has available to it, which I'm using the, um, hyphen, lowercase, dm,
capital S. Those are the three options that I'm calling into screen in order to create a socket
without, uh, being switched into the socket. Uh, you use the dm s capital S or with screen will
allow you to create a socket, but it will move you into that socket when you create it. Obviously,
I don't want to do that because I'm creating multiple sockets. So I don't want to be swapped into a
socket. Then have to leave the socket to then create another socket or end up in a problematic
situation where I'm inside of a socket, trying to create another socket. So you just create all
of the sockets that you need and then transfer into them when you need to. Now after creating the
sockets, we run an LS through screen, which allows screen to display the available, uh, so LS is
just list socket, uh, in, uh, bashes where you can see the L, LF. So the additional thing to check for
and what we're doing is checking if the user supplied in, which is no, then kill those sockets and
with screen, the way you kill a socket from outside of the socket, you would call the X for execute.
Then you would specify the socket with, you know, the capital S. So it's a capital X for execute,
capital S for, uh, specifying a socket, the name of the socket. And here's one of the one of the
things about when you're, uh, targeting a socket and screen, you don't have to use the full name.
So you can see with my socket names, I have it as apps for letters, APPS. Um, but when I want to kill it,
I could just do AP. I don't have to do the full APPS. Same thing with the jobby jobby. It's J-O-B-B-Y.
Uh, same thing. I just do J-O-B and then you could just kill it. You could also kill it by the P-I-D.
Um, because that's going to require a lot more writing to, uh, target the P-I-D, you can forget
about that. We're not doing that. Um, I used P-I-D. When I want to kill with a P-I-D, I do that a
little more manually, right? You know, certainly not. I'm not going to be doing all that bash just to
kill with the P-I-D. It's not necessary. And, um, we got our obligatory good heavens right down
there just in case somebody typed something other than Y or N. So if you try to put a Z in there,
you're going to get good heavens. And then the help menu will pop up, hopefully explaining that, uh,
you not do that the next time. And, uh, we got the S option down there in the case statement as well,
where, um, what does that do anyways? Okay. So that's just creating additional sockets that are,
you know, if, if for whatever reason I needed another socket, I could just run the S option
than the name of the socket would be the argument. So I'd be able to create more sockets if needed.
K is for killing sockets. So, uh, the K in that, which is being managed through case, I've already
talked about screens, uh, capital X, capital S options for screen. And I know I'm saying option for
both the script that I'm talking about as well as for the screen program. So, you know,
hopefully it makes sense if you knew just give the show another listen and, you know, if you check
the show notes, it'll be a little bit more clear. But there it is. And, um, again, those echo
statements are just sort of debug statements to let me know where it failed during the time that I was
writing it up. Uh, another thing that I want to pop out here, because we're down here at the bottom of
the show now. I'm all the way at the bottom. Uh, there's nothing to explain anything else except for.
I guess I could put a little bit more emphasis on the, uh, on the good heavens invalid input.
Obviously, if you put in anything that isn't listed within the case statement, you're going to get an
error. And you need a way to manage the error. And the best way to manage it is by, you know,
splash screen, good heavens, you know, uh, which there was a way to add a sound effect to where it
makes it sound like something thumping on your monitor on the, uh, the glass of your monitor.
Letting you know, like, hey, you did something wrong. Okay. Enough about that. And know that you
really don't need anything like that. I was just being silly. But, um, I just want to quickly talk
about indenting when you're writing in kind of script or coding or whatever. Uh, I still don't have
a clue how to indent, right? Like I, well, everything you see here is just what works for me.
My guess is there's no real, well, maybe there is because depending on where you're working, uh,
what project you're working on, they may have sort of rules about indenting. I've tried to
watch some videos on it. But, um, typically what happens is they use languages I don't understand
during the explanation. So I just get lost trying to figure out what the language is, what the code is
that they're using, what it's doing. And really don't take away anything about the actual indenting.
So, um, my understanding of it is that it's supposed to make the code a little bit more readable.
But even, even so, right? The actual practice is like the best practice of how far to indent before
you start getting into the, the good heavens range. Yeah, that, that is still not exactly a thing
that I understand. And maybe, maybe it'll be more understandable, um, with, with an
understanding of more languages. So as you learn more languages in the practice, it's from those
languages. You, you, you have a better understanding of how indenting is done. Maybe it's just done
differently in each language. So, uh, who knows, right? Or at least I don't know if you know,
there's a show. All right. Maybe you just have a technique you like to use and it may not be like
an industry standard, but you use it and it works out just fine. There you go. So if you've ever
wanted to write a script and be able to do the little dash options to supply it to your script,
now you have two good examples on how you could, uh, accomplish that. And you're welcome.
Go ahead and leave a comment down below or do a show as a, uh, comment. And I'll catch you guys
in the next episode of Hacker Public Radio. Thank you. I'm some guy on the internet signing off.
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