Tag: bash

Avoid Storing Commonly Used Commands In Your Bash History

This article won’t need to be all that long but it might be complicated as we discuss how to avoid storing commonly used commands in your Bash history. Yes, it’s a long title. 

This is also a bit contrary. It is one of those things that is easier done than said. It’s a very wordy thing, after all. I’ll do my best to describe what’s going on and why you might want to do this.

In this case, Bash stands for Bourne Again Shell. This article only applies to those who are using Bash. Bash is not the only shell available and people may opt to use other shells. If you’re one of those people, I don’t think this is going to work for you.

When you’re using the terminal, you’re using Bash. The commands you enter into the terminal are stored in ~/.bash_history, a hidden file in your home directory. We’ve discussed some of this before.

How To: Have Infinite Bash History
Playing With Your Bash History
How To: Not Save A Command To Bash History
How To: Reload Your .bash_profile

Well, you may type common commands, such as uptime. You may not want to store that command in your Bash history. Do you want to store every time you’ve typed the ls command?

You don’t have to. You have options!

What can you do? Well, you can tell Bash not to store certain commands in the ~/.bash_history file. This is actually a simple operation. To avoid storing commonly used commands in your Bash history, you need only to edit your ~/.bashrc file. I’ll show you how!

Man, this is going to impact the layout…

How To Avoid Storing Commonly Used Commands In Your Bash History:

Yeah, no amount of formatting is going to make that look good.

Anyhow, if this isn’t obvious, you’re going to learn how to do this in the terminal. You could edit your ~/.bashrc file with your favorite GUI editor but we’ll be doing this entire thing in the terminal.

As such, you should have an open terminal. More often than not, you can open your terminal by pressing CTRL + ALT + T. If that doesn’t work, you can find a shortcut to your terminal in your application menu. Should that not work, you’re probably already in the terminal!

So, first, we need to use Nano to edit the ~/.bashrc file. That’s an easy command:

Use your arrow button to navigate to the bottom of that file. Go to the absolute bottom and press enter to start a new line. You can press that button twice to provide some separation and to make it easier to read.

Now, let’s say we don’t want to store the ls, uptime, or touch commands in your Bash history file. We’ll use those as our examples. You should also probably leave a comment in your ~/.bashrc file so that you can easily identify what the code does and remember why you added it. That’s also useful if there are other users.

So, add the following lines:

Next, save that file. As we’re using Nano, you save the file by pressing CTRL + X, then Y, and then ENTER on your keyboard.

Next, you reload your ~/.bashrc file much like you reloaded your Bash profile (which was a link in the intro, should you wish to read it). You reload the ~/.bashrc file with this command:

That should reload the file. If it doesn’t, you can close all your terminal instances and open a new one. If that doesn’t work, you can log out and log back in again.

Anyhow…

Commands starting with :<command>: entries you used will not be stored in the ~/.bash_history file. If you type a command starting with those entries, it will be ignored, meaning they won’t clutter up your ~/.bash_history file with commands you’re already familiar with or commands that don’t need to be stored for things like auditing or security reasons.

It’s pretty simple to do, though it’s a bit of a pain in the butt to explain. This is how you avoid storing commonly used commands in your Bash history – something nobody is going to search for. (If you did find your way here via a search engine, be sure to leave a comment. I want to know who you are!)

Closure:

I realize that this is an awkward article and I’m okay with that. This isn’t something everyone is going to bother with, especially those people who don’t do much in the terminal. Still, it’s possible to avoid storing commonly used commands in your Bash history and now you know how.

Then, someday, someone’s going to search for this exact string of characters and, hopefully, they’ll find this article. I hope this satisfies their curiosity and helps them reach their Linux goals! If you did read this and find it valuable, you can always leave a comment.

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Playing With Your Bash History

Your Linux computer, assuming it’s ‘normal’ will retain the commands you typed in the terminal and this is your Bash history. Like all things Linux, this is something you can control. The ability to customize these things is one of the things that makes Linux great!

More specifically, this article will cover how to change the Bash history size. That’s one of the things you can control. It’s one of the settings you can customize. You don’t have to accept the default Bash history size. It’s easy enough to change those settings to whatever you want.

I’m going to assume ‘normal’. That is, normal to me. I’m going to avoid the word ‘standard’ because I don’t know if these things that are normal to me are standards. For example, even the Bash shell isn’t a standard. However, it’s normal for a Linux distro to provide Bash – typically as the default shell. It’s not a standard, it’s just normal. That is, normal to me.

Got it?

Well, your Linux computer usually uses Bash shell. It also normally keeps a history of commands you type. This file is normally a hidden file, called .bash_history and is a plain text file. 

Bash has a control file. That is, Bash has various settings that can be configured. This file is also normally hidden. It’s usually called .bashrc. As this is about the shell and Bash, you will need an open terminal to follow along with this article. You can normally just press CTRL + ALT + T to open a terminal.

What is the Bash shell?

Bash is a Unix shell. It stands for Bourne Again Shell. It has long since been ported to Linux and is what you’ll normally find when you look into the more popular Linux distros.

A shell is a command line interpreter. It’s a user interface that lets you interact with your computer in a text-based manner. There are other shells besides Bash, but this article isn’t going to cover any of them.

This article presumes you’re using the default Bash shell. If you’re curious, here’s a big comparison of shells. Some people like to use different shells with csh and and zsh being popular choices. 

Bash is just one of many possible shells, but it’s normal to see Bash as the default. If you’re not using Bash, this article may not apply. You won’t see me writing much about other shells, as I’ve mostly just used the default shell rather than spending time exploring other options.

Bash History:

As mentioned above, you usually have a .bash_history and Bash usually stores the commands you’ve entered in that file. That file is plain text, meaning you can search it, edit it, or even modify it. I’ve written some about Bash’s history before.

Search For Command History By Date
Dealing With Duplicates In Your Bash History
Let’s Delete An Entry In Your Bash History
How To: Not Save A Command To Bash History

This shouldn’t be a foreign concept to my regular readers, though I’ve not written much about Bash recently. This seems like a fine time to cover this subject.

Today, we’re going to change the Bash History Size. There are three variables you’ll need to know. Well, you can get away with just knowing two of them, but we’ll learn all three.

Bash History Variables:

As I said, there are three variables we’ll be using to control the size of your Bash history. They’re all pretty simple and they all control one aspect of the Bash history.

HISTFILE:

The first variable is ‘HISTFILE’ and you can echo this to get the information. The file is normally located at ~/.bash_history but you could change that value and have the history file anywhere you want. You can find the Bash history location with this command:

The output would look similar to this:

HISTFILESIZE:

The next variable we’ll concern ourselves with is ‘HISTFILESIZE’. This is how long, specifically how many lines, will be saved in the .bash_history file. You can your current configuration with this command:

Again, the output from that command might look similar to this:

That means the .bash_history file can be up to 2000 lines. That’s quite a bit, but not far from normal. I think I’ve messed about with it before, so I’m not sure if that’s the default. Just echo the variable to find your current settings.

HISTSIZE:

The next variable is going to be  HISTSIZE which is how many lines your shell should retain in memory. If the HISTSIZE is set to 20, you’ll have 20 lines of history to scroll back to visit. You can get the HISTSIZE settings with this command:

An example output might look like this:

NOTE: This can sort of be overridden by your terminal client. If you have a $HISTSIZE of 1000 and your terminal preferences (some terminal emulator clients have this setting) are set to 500, you’ll only have 500 lines kept in the cache at any one time. However, the number of cached commands is still 1000 – but your terminal will not show them.

We can change these variables!

Change Your Bash History Size:

Now that you know the default size settings for your Bash history, you can go ahead and learn how to change the settings for your Bash history. While it’s possible to change the location of your .bash_history file, there’s no need to.

We’ll worry about our Bash history size, that is how many lines the history file will hold. Anything else is superfluous so we’ll skip it.

The first variable you might want to change is the total number of lines that will be stored in your history file. That’s done like so:

If you want your Bash history to hold 5000 lines, the command would look like the following command:

That won’t take effect immediately. You’d have to reboot or close all the terminals before opening a new terminal for the new settings (reloading what is normally called .bashrc) to take effect. However, you can force the issue with the following command:

If you want to change the value for the maximum number of cached commands a shell can retain in any one setting, you can use the following command:

If you wanted to match the HISTSIZE with the new HISTFILESIZE, that’s easy enough to do. Just enter the following command to change the value for HISTSIZE:

Just like before, you’ll have to tell Bash to reload your settings because they’ve changed. Rather than close things, log out, or reboot, just enter the following command for the HISTSIZE change to take effect immediately:

Note that none of these commands require sudo. If you are having to use elevated permissions, you’re doing it wrong. Well,  you could be modifying the settings for another user but that’d take direct editing of the .bashrc file and you’re better off modifying that file when logged in as the user.

Closure:

Well, that was a pain in the butt to write and format. I hope that it’s not too confusing. I kept typing the variables wrong and this article about changing your Bash history settings required quite a bit of advanced formatting. That takes time, which means this article took time. Still, I wanted to cover the Bash history configuration choices and I wanted to do them all in a single article.

This article is much longer than my normal articles. I dare say that I’ve changed my writing style – again. I’ve been doing longer format articles. Previously, I’d have only covered the $HISTFILESIZE variable and left it at that, without adding many links or much additional information. I do welcome feedback and suggestions.

If you don’t like the longer format, say so. If you do like the longer format, say so. Hell, if you read the closure section say so! I don’t know if I’ll change much based on the feedback, but it’s good to know. Lately, I’ve been pulling down quite a bit more traffic, so something must be working. I’m no SEO expert, so I do what I can and follow directions from people who have had more success. But, the site is coming along nicely.

Amusingly, I’ve had almost no emails on the advertising subject since I added the Sponsorship link. I should mention that it’s possible to sponsor an article even if you’re not a business. I’d just put in a ‘thank you’ notice and link to pretty much anything you want if you did indeed want a link. This site has a solid reputation, but it’s still growing – and growing pretty quickly as of late.

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How To: Have Infinite Bash History

Today we’re going to have a good time because we’re learning how you can have infinite Bash history. There’s a bit more to it and not all of you will want an infinite Bash history. But, for those that do, we’re going to accomplish that right here in this article!

First, I’m assuming you’re using Bash as your shell. The odds are really good that you’d know if you’re not using Bash, as Bash is pretty much the default. Bash is the interactive shell you’re using, known as Bourne Again Shell. If you don’t know what shell you’re using, I covered that in an article about determining the shell you’re using.

Side Note: I sometimes write articles that are meant to preface another article, but then I forget and don’t write the additional article. I suppose that helps keep things interesting…

So, as you know, when you type a command into the terminal that command is stored in a file typically called ~/.bash_history – a hidden file in your home directory. Well, there’s a limit to how much history that file will retain and this is Linux – meaning that, of course, you can change that value. Today, we’ll be changing that value – making it ‘infinite’.

No, of course, it’s not really infinite. There’s a finite amount of disk space you have. This being a plain text file, it takes up very little space. While it’s not technically infinite you can store a whole lot of entries in your Bash history. We’ll set it to infinite, but I’ll show you how to set it to any value you want.

Ready?

Infinite Bash History:

As you can see, this is a Bash thing. That’s a good sign that you’ll need an open terminal. You can press CTRL + ALT + T and your default terminal should open. See? We’re already making progress!

With your terminal open, we’re going to edit another hidden file. The name of this file is .bashrc and it’s a file that stores things like terminal settings.

The tool we’ll be using is ‘nano‘. Click that link to learn about Nano, including how to install Nano should Nano not come preinstalled in your chosen distro. As you may know, Nano is one of my favorite text editors. We use Nano a lot around here.

Start with opening the ~/.bashrc file with nano, like so:

Scroll to the bottom and add the following lines:

Any negative value, in this case, -1, will result in an infinite history. However, you can make that value any number you want. When you’re done adding those lines, you have to save the file. Remember, to save a file in Nano, you just press CTRL + X, then Y, and then ENTER.

You could make the value 5000, for example. That’d simply look like this:

The sky is the limit. You can make that value any number you want, but all negative values will be treated the same. If the value is negative, it means you’ve got an infinite Bash history. Don’t forget to save any changes with Nano, as instructed above.

Now, you could reboot or log out to make the new settings take effect, or you can simply tell your system to reload the file to make the changes take immediate effect. That’s an easy command, simply use:

As you can see, infinite isn’t infinite (nothing is in the real world, according to current observations) and you don’t have to choose the infinite setting. You can pick whatever numbers you fancy and the process is the same.

Closure:

There you go, you now know how to set up your system to have an infinite Bash history. Well, an infinite ~/.bash_history if you prefer. With that setting engaged, you’re limited only by your creativity, fanaticism, and disk space. Go nuts with it! They make bigger disks! (Also, it takes up very little space.)

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How To: Not Save A Command To Bash History

Today’s article is another short-form article, where the subject is how to not save a command to bash history. It’s trivially easy and something everyone can learn. So, read on and learn how to not save a command to Bash history.

The vast majority of my readers are going to default to using Bash. 

bash – GNU Bourne-Again SHell

You’ll access Bash through your terminal and, again as the default, will save x-amount of past commands to a file known as ~/.bash_history. Anything you enter as a command (though not passwords entered at the password prompt, as that’d just be silly) will be saved to that file.

If you’re like me, you use the terminal a great deal. Again, if you’re like me, you value the Bash history aspect but you don’t want it full of trivial or experimental nonsense. You can prevent a terminal input from being saved in your ~/.bash_history – and it’s trivial to do so.

Do Not Save A Command To Bash History:

Seeing as I’ve been doing short-form articles for the past couple, this one seemed like a lovely tip to share with my readers, as I’m sure some will not know this. 

Of course, you’ll need an open terminal for this. Press CTRL + ALT + T and your default terminal should open.

With your terminal now open, we’ll use the ‘ls’ command to list the contents of your present working directory. Ready?

Now, that’ll be saved to your Bash history file. What if you don’t want it saved to that file? Just add a space in front of it, like so:

I don’t know how well that will show up, but trust me when I say there’s a space there. By adding that space, I’ve effectively told the terminal to not save that entry into the history file.

See? Pretty darned simple!

Closure:

So, yeah… I’ve been doing a few short articles and this seemed like the perfect article to do in that format. It’s something not everyone knows, isn’t made immediately obvious, and will likely be of importance to someone. If you’ve ever wanted to not save a command to bash history, that’d be how you do it.

I could have added a few more bash tricks and turned this into a longer article, but I’m having fun with this shorter stuff right now. If you prefer the longer articles, don’t worry. They’ll be back soon enough. These short articles are fun and easy, and they have the added benefit of keeping me interested in writing these silly things.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment. 

Disable Specific Terminal Commands

In today’s article, we’re going to learn how to disable specific terminal commands. It’ll be an interesting article because we get to explore some different tools. It might get a bit verbose, but I’ll do my best! It’s going to be a long article, but I’ll try to keep it at under 1500 words.

It should be noted that this is for people using the bash shell. As I don’t sway too far in that direction, I can’t vouch for it working with something like ZSH or similar. I simply haven’t tested. Feel free to try. I know some of the shell alternatives are compatible so you can check.

Read on to learn how to disable specific terminal commands!

Let’s say you don’t want your computer users (or you yourself)  to run a command in the terminal. Well, you can stop that command from being run easily enough. To do this, we’ll explore some new concepts and tools. One of those topics is ‘aliases’. Let’s just start there…

About Bash Aliases:

In short, bash aliases are alternate ways to enter in a terminal command. You type one thing and the system interprets it as an alias for another command. Let me explain this bit further.

Let’s say you want to run the following command:

Well, if you wanted to, you could assign an alias for those commands. If you wanted, you could even change your aliases so that all you had to type is:

You’ll run the full command when you’ve entered the alias. Aliases are basically little shortcuts to other commands, often used when you want to enter the command quickly and it’s a longer command. You can more or less alias anything with anything if you put enough effort into it.

Getting Ready For Aliases

Still with me? Alright, now you need an open terminal. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

With your terminal now open, let’s check to see if you already have the necessary file. I am aware that you can just add aliases to your ~/.bashrc file, but this way avoids clutter and is more easily portable.

So, we need to check to see if you have ~/.bash_aliases. You can run the following command (from your home directory) to see if you already have the file you need. Simply run:

Now, scan the output from that command. Do you see a .bash_aliases? If so, skip ahead. If not, you will need to create the file yourself. One way to do so is by using the following command:

That command will create a blank file (named .bash_aliases) in your ~/ directory. It is the only file we needed to create and will be the only file we need to edit. You’ll also use nano, which my readers should be familiar with already. Don’t close your terminal yet, we’re still going to need it in the following section.

With just a few tools, we’ll learn how to stop specific terminal commands.

So then…

Disable Specific Terminal Commands:

I had to write that giant intro just to get a newbie up to speed. I’ve been meaning to explain aliases for a while, but I suspect the topic will get its own dedicated article. It’s a pretty broad subject.

For this next session, we’ll use a harmless ‘uptime’ command. Let’s just run that in the terminal just once:

Now, for whatever reason, we will have to pretend that you have decided you want to disable specific terminal commands and uptime is one of those commands. To do that, you’ll start with the following, editing the file you just created:

You will want to start a new line and the command is formatted like so:

For example, you can have an alias like this one:

Save the file with nano. It’s not too daunting a task to save the file. To save a file in nano, all you need to do is press CTRL + X, then Y, and then ENTER

In the above example, if you were to type ‘myip’ into the terminal and run it, it’d almost run the command you told it to run.

You’re almost there. There’d be just another step.

You’ll have to reload the aliases before the system recognizes it as such. I’ll explain how to do that in a second.

Now, if you want to disable specific terminal commands all you need to do is fill the <command> section with a blank space or two. As it is our example, we don’t want the user running this uptime command, it’d look like this:

See? Not all that complicated and we’re almost reaching the end – just one step further and your new alias will work as you’d expect – or not work, as one would expect in this case.

Make Your Alias Permanent:

First, to make that alias stick around you need to have saved the updated ~/.bash_aliases file as was explained above. At this point, the alias will not work. The file you wrote isn’t loaded into memory. It takes a bit more than that.

From here, you could close all your open terminals, log out and back, or reboot – any of those will reload your bash aliases. Alternatively, you can run the following command, which will refresh your terminal’s list of aliases. Like so:

If you’ve done everything properly, you’ll find that this happens when you try to next run the uptime command:

the user is unable to run a specific command - in this case the uptime commnd
That’ll teach ’em from trying to run that pesky uptime command! Catastrophe averted!

But…

If you want to disable specific terminal commands, you might be wanting to do so for security reasons. The ~/.bash_aliases file is owned by the user, so the user can just edit the .bash_aliases file to remove your edit.

So, what can you do? You can make it permanent for everyone. You can add it to /etc/.bashrc, and a user with limited rights won’t be able to edit the file. If they can’t edit the file, they won’t be able to remove the alias. They won’t be able to use the terminal command(s) you’ve aliased to nothing. If you were to simply edit the /etc/bash.bashrc you’d just start a new line at the bottom and then insert the aliases using the same format. 

I haven’t tested it, but I’d wonder if /etc/.bash_aliases might also do the trick in preventing user edits to override your changes. Feel free to test and then let us know. It’d be interesting if you could do something with /etc/skel/ and changing the file permissions – effectively for new users created.

Closure:

There… I think I’ve covered everything. I’ve wanted to write about the bash aliases subject for a while, but it’s just a bit complicated to explain. So, I figured I’d write this article. It’s a long one, but there’s a whole lot to cover. This goes into it pretty heavily, but an aliases-specific article might be nice to have.

Either way, you can now disable specific terminal commands. You can probably temporarily lock yourself out of your own system, so be careful with what aliases you add as system-wide aliases.

If you do lock yourself out, you should be able to boot to a live Linux disk where you’ll mount the drive and just revert your changes. But, anyone with physical access to your computer owns your computer, which is worth keeping in mind.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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