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Why are there no extensions for text documents in Linux?

For example when you see something like /etc/issue how are you going to know that issue is a file -- text document -- or a directory?

Sometimes this becomes confusing for me since I just open up a file manager and try to navigate, I don't know if I should look for a folder or a file and maybe that's because I'm new to Linux environment?, any tips?

Shayan
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    Not a really a duplicate, but file extensions don't really matter in GNU/Linux. – pomsky Feb 17 '18 at 21:04
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    ls -la is your friend. If you see starting d it is directory. In GUI folders and files are visually different as in windows (but files may not have extensions, it's normal). – N0rbert Feb 17 '18 at 21:07
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    Tip: You get used to it. Embrace the difference, and the flexibility that Linux filenames offer. – user535733 Feb 17 '18 at 21:09
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    "Why are there no extensions for text documents in Linux?" because fileextensions are not used for recognizing what a file is about and can be abused to trick someone in believing it is not what it is. "execute.txt.exe" in windows looks like a txt file but when doubleclicked can install software. – Rinzwind Feb 17 '18 at 21:16
  • Ty all for your answers, I mean comments sorry xD – Shayan Feb 17 '18 at 21:18
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    If unsure, ask your system with file /etc/issue (sorry if this was in provided link, I didn't see it). Sure its not perfect (old bug on can't print on tuesdays 255161) but its pretty accurate and is less error prone than users adding a filetype by adding .txt to signify text. – guiverc Feb 17 '18 at 22:03
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    @guiverc That helps a lot! file /etc returns /etc: directory and file /etc/issue returns /etc/issue: ASCII text Thank you! – Shayan Feb 17 '18 at 22:46

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Depending on your way to look at files, it is easy to distinguish, by icons, by conventions, by small indicators.

Many of the comments are to some degree true, but nothing is sufficient as an explanation.

  • On Windows, you may create text files without extension. There is no mandatory requierement to use extensions.
  • "Why are there no extensions for text documents in Linux?" There are. On my system, a lot of them, .txt, .csv, .sh, .scala, .java, .sql, .dat .svg, .xml, .html and many more. Many of them indicate more, than just that it is readable text. None of them is a guarantee.
  • You are even allowed to name a directory "foo.txt", and guess what - it's possible on windows too.
  • "execute.txt.exe" is of course a trap, but only problematic, since windows introduced hiding of the suffix (only the last one) and deciding by extension, how to execute a file. Unixlike Systems have permisssions, one of them is, to execute a file, and then the system will try to execute it. It's not a guarantee, that it is possible, either.

In the shell, you can get a long output format like:

-rw-rw-r--  1 stefan stefan    2184 Feb  5 04:27 ShortestPalindrome.java
-rw-rw-r--  1 stefan stefan     283 Dez 20 03:58 speedtests.lst
drwxr-xr-x  4 stefan stefan    4096 Nov 28  2012 src
-rw-rw-r--  1 stefan stefan    2609 Jan 16 23:01 Stringkuerzen-2018-01-16_23:01:27.java

with ls -la. The first character 'd' tells you, it is a directory.

Just using ls gives you a brief list. Then the color, which is set up by default, indicates which file is what, especially directories. If you don't fiddle around with it, it should work fine.

Linux has the 'file' command, to make an informed guess, what kind of file a file is, and most of the time this is right. But it can be fooled too. Not as easy as the windows extension system, but it can.

However, naming your PNG-files winter.png, your text winter.txt and a shell script winter.sh is still a good idea, because it is user friendly.

A file browser, like Thunar, will indicate which kind of file a file is, by Icons in the icon view, smaller icons in the list view, and smallest icons in the compact view. Often the sort order is placing directories first.

The midnight commander has it's own way of indicating directories in bright color. I guess most file managers do it in the one or other way.

But in contrast to other files, directories can't be mocked (except from symbolic links, which is a different topic). The type directory is deeply fixed in the system - you can't 

cd abc.txt

if abc.txt isn't a directory. And yes, it can be, but most of the time it shouldn't.

With much effort, somebody could generate a program, which would catch the error, to step into a file instead of directory, which could be useful, if the file was an archive, for example, but on the shell I haven't seen such a thing.

And a directory can't hide it's nature. But that's the same for windows too, isn't it?

Conclusion: Most of the time, extensions are useful, but they guarantee nothing. If you have files from trustworthy sources, you can rely on them, if not, the file command is a good help, but no guarantee either.

This is a sample output of

file * 
funreturn.scala:                              ASCII text
hexcodes:                                     ASCII text, with very long lines
inkscapepfad.scala:                           FORTRAN program, UTF-8 Unicode text
iterfind.sh:                                  Bourne-Again shell script, ASCII text executable
leaderbord.aoc:                               ISO-8859 text
lib:                                          directory

The guess, that inkscapepfad.scala is a Fortran code, is just wrong, and relying on the extension would here have been the better choice, and that, without intend to fool file, just by incident.

user unknown
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