File extensions are a horrible anachronism. I can’t understand why they’re still needed in most cases (all binary files should have a specification which mandates the use of a magic number - that some don’t just means that the specification of these outliers needs updating).

In fact the only possible use-case I can see is for text files which might contain different content (c code, c header) but even that might not be necessary in many cases - it should be possible to identify html or xml just by looking at the first few characters.

Extensions and the workaround of enabling them to be hidden just brings confusion and dismay. It’s a nasty throwback to the days of CP/M!

They are handy for humans to see from a list of files what they might be.

But equally they are a dumb idea to use for what happens with them once you get in to execution of binary/script. And DUMB with a monster-sized D when you look at MS's bone headed idea of hiding the extension but still using it to decide what to run if double clicked. Morons, morons, morons...

file.txt.exe or file.pdf.exe being favoured filenames amongst those attempting to hack into computers, of course. If you're paying close enough attention, you might spot the duplicity, but it's easy to miss. Dumb UI choice, presumably in the name of "simplicity".

Dumb UI choice made by Marketing overriding Engineering, something that never should have been allowed but, Ballmer.

'Nuff said.

"MS's bone headed idea of hiding the extension but still using it to decide what to run if double clicked."

I'd used KDE's Create New facility to create a LibreOffice text file but not noticed when I renamed it that I'd overwritten the whole of 'LibreOffice Writer.odt' instead of just the first part, leaving it without the extension. LO opened it OK and saved it, the GUI showed the correct icon. Nothing I used needed to see the extension to know what it was. I didn't notice at all until someone I'd emailed it to replied to say she couldn't open it with LO in Windows.

"it should be possible to identify html or xml just by looking at the first few characters" so you have to open the file??? Trusting the OS to identify it is recipe for disaster and doesn't work in a text interface.

How about you have a simple convention, say a 3 letter label on each file so it's easily human readable in every context to at least get an idea of what it contains BEFORE you look inside it.

They never should've been hidden imho, that way lies pain and confusion.

"it should be possible to identify html or xml just by looking at the first few characters" so you have to open the file??? Trusting the OS to identify it is recipe for disaster and doesn't work in a text interface. That's literally what the `file` command does.

Reading data from a file is not inherently dangerous. What's dangerous is executing instructions from an unknown file.

This is true. But even reading data can be dangerous - although I’m don’t know of any vulnerabilities in file off the top of my head.

But I really shouldn’t be thinking at all today.

> This is true. But even reading data can be dangerous - although I’m don’t know of any vulnerabilities in file off the top of my head.

There have been a couple of "text of death" type bugs in Android and iPhone that meant nasties could happen simply by receiving a text. And there has been at least one image format exploit where opening a crafted image triggered a buffer overflow exploit. And, most recently, even logging (in Log4J) data can cause grief.

"That's literally what the `file` command does."

Yes, but you're talking about a real operating system there.

@ali dodd

Damn! Absolutely correct - have a thumbs up. Of course it could be unwise for the OS to have to probe into each file to get its type. That way malware lies. So the only issue is the hiding of the extension.

So obvious. So right. I’m going to blame my previous oversight on the fact that I’ve currently got Covid and any thinking is hard work.

(Shuffles back to bed in disgrace)

So obvious. So right. I’m going to blame my previous oversight on the fact that I’ve currently got Covid and any thinking is hard work.

(Shuffles back to bed in disgrace)

Is that what is meant when people mention COVIDIOTS?

Get well soon.

It should be safe enough for the OS to look at a few bytes to look at the magic number or other diagnostics.

I find file extensions incredibly useful for organising things. For example, right now I'm doing some design work for a couple of projects, and I have Project1.docx and Project1.pptx open alongside Project2.docx, Project2.xlsx and project2.pptx

Nowadays, file extensions are not really used by the computer — they're used by humans who want to know the file format. It's a buggy system, since the extensions can be wrong. The Word document can have .txt extension, the .html file can be a JPEG.

When you are using a GUI, you can have icons that do the same job, but you are not always using a GUI; the GUI often just repeats what the extension claims without checking; and the GUI might not even understand the proprietary format.

But personally, I'll keep using extensions. I'd rather have some indication of what the file format is, and hope it was set properly, rather than having to guess every time.

Of course, that never stops people thinking they can change a file type just by changing the extension. I had that recently on a website I built for a client where one of the client's staff had "helpfully" renamed some PNGs to a JPG extension and then complained that some resizing code wouldn't work on the affected images. I added a "deep code" check along with a warning when images were discovered with the incorrect extension.

Magic numbers are not reliable either. There is no universal location or format for the magic string and so files can and do get misidentified. At least with extensions they are under the control of the user.

There are plenty of other cases too, such as layered formats such as .tar.gz or formats that package multiple elements in a single .zip. Using magic all you see is the outer container.

Finally it's an expensive way of doing it. Every file needs to be read and compared against a long list of possibilities. What if you are looking at a remote FTP server for example where you want as many clues at the directory level as possible.

surprised it took that long. The first thing I do when logging onto any server is check that explorer setting

You would like to think that any admin account, and ANY account on a server, would not be used by people afraid of file extensions, so would be disabled by default?

That and unticking "Hide system files".

I remember when Microsoft did that trick of hiding the extensions, I was working on something using file names like:

projectname.txt

projectname.doc

projectname.xls

Oh fun! Yes, I could have learned to differentiate the subtle variations on the icons, but life's too short: I enabled extensions.

I could have learned to differentiate the subtle variations on the icons, but life's too short

Not only is life too short, but so is my sight - in a lot of views the icons are too small for me to make out at a glance which is which.

The icon showing is dependent on the associated program - hence with only a little nefarious fiddling you could have all the icons the same as well.

I think you only get the option(*) to associate a program now, so you get the icon for that program... used to be fun trawling dlls for useful icons

(* at least I haven't seen the option in Win8/8.1/10)

Oh yes. The hidden file extension must have worked so well, that Mirosoft decided to build the whole control panel for Windows 10 the same way.

They are useful for ordering data in a directory / folder / whatever you want to call it.

Very handy to search by extension.

Only problem with filenames is windows default of hiding them, irritating when app, config file / manifest etc then all appear just as the same name (as only the suffix identifies the difference)... and Windows irritating icons for identifying file type are far from ideal.

I honestly can't think of a good reason for hiding file extensions in the first place. Not one.

A pint of --> for anybody who can.

File extensions can be changed using the rename function. If they're hidden then they can't be changed. It removes the opportunity for fuck ups.

It allows miscreants to send you Word.doc.exe and you see Word.doc and you execute it.

A big, fat FAIL in my book.

I prefer the opportunity for fuckups - they're my fault.

To look more like Apple?

Yes, I get that people's opinion on whether being more like Apple is a good or bad thing may vary but, around that time, Apple's look/feel and general user experience (for the non-techy at least) was better/cleaner. Personally it's not my taste but for many (e.g. my mum) picking Apple over Windows was a no-brainer and I think MS wanted to try and get some back.

"To look more like Apple?"

I just checked and at least on Monterey you can hide extensions on a per file basis....

what fun?

In my IT job over 12 years, a lot of the users were a bit clueless, and for some reason a lot of them used MS Word 'open' file dialogue to browse/search for files.

Of course, the file naming convention was just a stupid - a lot of word/excel names were the same, so all the files looked the same.

Enter the guessing game. The amount of times they opened excel files in word, and now the checkmate - the first thing they did was SAVE IT!

In the end my boss told me to ignore any request to restore these files.

I've been railing on this "feature" since the Windows ME days at LEAST. Working front line support for an OEM, and having to talk grandma and grandpa through finding a file and the extensions are hidden is a nightmare. It got to a point that one of our first support steps was to disable "Hide file extensions for known file types" early in any call, and when reinstalling Windows would have the customer do this as soon as possible.

Oh the fun caused by those dodgy 'file save' dialogues, where selecting something like 'file type: *.txt' then typing 'credentials.txt' would save it as 'credentials.txt.txt'

And the fun of forgetting to set the correct 'file type' then discovering 'credentials.txt' is saved as 'credentials.txt.rtf'

Yes, hiding file extensions really was a brilliant marketing idea.

Eh, Ballmer ?

Conversation with a usually competent colleague:

Him: I can't import this certificate

Me: Oh really? Let's have a look...

[Quick screen share]

Me: Right, so what you've got isn't cert.crt, it's cert.crt.txt, turn on your bloody file extensions

Him: D'oh, thanks, sorry Outski and rest of the team whose time I've wasted

----> one of many beers owed by the left pondian team for dumbass mistakes

I wrote a nice web app where suppliers could upload data straight into our systems from a CSV file, to save me from 20 minutes of mucking about with awk every time anybody e-mailed us a spreadsheet. I already had a collection of headers, so I used them to make it smart enough to work out -- within limits, but those limits were still pretty broad -- which column was what.

Within minutes of putting it live, I had a customer on the line insisting that it was not accepting their .csv file.

It transpired that, instead of following the clear instructions with screenshots showing where to change the file type in OpenOffice.org Calc and Excel, they had simply used whatever the Windows equivalent of `mv` is to change the extension of an .xlsx file .....

Unfortunately, being stupid is not a disqualifying criteria for using a computer.

And if you think that just changing the file extension from xlsx to csv changes the file format, then you're too stupid to use a computer.

More unfortunately, there are many, many people who haven't got a clue what a file extension means, but they're still employed and using a computer.

That's the employer's fault : he doesn't know what a file extension means either.

On the mainframe we had to worry about sources files in ascii and EBCDIC, and there was a setting which set the code page on the file. The various zip/pax commands did not always work.

Our simple instructions gave a nice little process for doing the work.

Some "clever" Windows expert thought 'I can do this with less typing and make it "quicker".' as a result his data was always in the wrong code page.

My colleague was on the phone for an hour trying to work out what the problem was.

The end of the conversation went

"Do step 1"

"Ok I've done step 1"

"Are you sure?"

"Yes"

"hmmm - what was the response from the command"

"xyz"

"But that's not the response from the command. It looks like you used the abc command"

"Well it works just well"

"No it doesn't it. Follow the instructions"

"OK Ive done step 1"

"Now do step 2"

"what response did you get?"

"That's not the response from the zyx command"

Loop:

Every file should have (a) an extension and (b) a version number. VAX/VMS roolz ok.

VMS did have it's problems though, since devices and files were analogous.

Back in the mists of time when I worked at the local college (now university) we had a student type up a long dissertation about an on-site facility then save it, unfortunately she used the facility name which was also a printer in that facility.

Result was no file and a student in tears.

Once we figured out what had happened we retrieved the print out and got one of the department secretaries (I told you it was a long time ago) to retype it and save it under a different name.

I've gone through the process of explaining to the noob about the possibility of the file extension being missing, wrong, or hidden. Use 'file wibble.xxx' and you'll get a fair idea of what you are dealing with, not infallible but good for 95% of cases, I say. That's magic they say. Yes it is: 'man 5 magic'.

An ICI power station many years ago with a snazzy new VAX 11/780 optimising the combustion process. VAX/VMS introduced version numbers, so the filenames were all in the format filenames.ext;version (IIRC 9.3;3 characters), every time you edited a file it was saved in a new file with an auto incremented version number which saved many people's bacon over the year.

Space was always an issue as the HDDs were only 128MB, so the OS provided a handy utility to purge the old versions down to a sensible level.

The designers of the system came from PDP land and decided that these newfangled version number things could be utililised for something more useful. So cue a directory filled with files named thus:

tempinput.dat;1

tempinput.dat;2

tempinput.dat;3

.

.

.

tempinput.dat;150

Each one contained all of readings taken every 15 minutes for an individual sensor.

I (being a newbie muppet at this point) typed PURGE/KEEP=5 across the entire disk and left the scene of disaster chuffed at the amount of space that I had recovered.

I hate that setting, first thing I change when working on a system.