what I meant by 'File extensions is useless in Linux is this

pico -w my.anything
======= write inside it
#!/usr/bin/perl

print "Hello world\n";

=== close it (CTRL + X) & save it.
chmod +x my.anything

now you can run it ./my.anything

and it will execute your perl script.

* you can even name it my.jpg & it will execute your perl script
[download]

I am using Ubuntu Netbook, I have many images saved without extensions ... and it works that way.

* you can even name it my.jpg & it will execute your perl script

..... yes, the basic linux filesystem has file permissions..... not file extensions... to determine if a file is an executable..... this is far safer than extensions as you are beginning to find out..... you probably are coming from a MSWindow's background and need to learn more about the improved security of linux....

it probably is getting crazy for you, if you are running a dual boot with linux and windows..... then you will start seeing files from the Windows OS, that seem marked executable, or vice versa... or you do alot of double-clicking on icons and expect the system to do what you want".. :-)

.... the way it works on linux is:

....you instruct your shell to execute a program, and regardless of it's name it will see if its marked as executable by you or your group..... if it is...it tries to execute it.... but if you try to execute a jpg or bmp.... it won't run....and will just return an error...... and then there are the shebang lines :-)....... maybe read linux programming... and the Rute User's Guide

...that brings us to default programs and apps which will properly load your file....its a part of your system setup....ubuntu uses the Gnome Desktop to determine file types thru a MIME-information setup..... first look for extension....then check type with a file-like command

...this is all getting to the point of you needing to read up on linux....it isn't a Perl problem

...see monitor suid and world writtable files for an example of checking perms.....

....also on ubuntu....try installing the program Midnight Commander, go thru it's menus and see what info is tracked on files

I have many images saved without extensions ... and it works that way.

...sure it does..... but that is because the Ubuntu Desktop handles it all for you..... as a matter of fact, your only problem may be that you have a destop setting set to hide file extensions, like they do on Winblows

why don't you right-click on those images and get the info?...... are you trying to automatically rename something like the browser's cache of images? :-) which are named like numbers?

..... you need to learn how Desktops work...... it's actually a program that has MIME type records built in..... go see MIME modules for Perl

---

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku

...dude your....style of..........writing is..............really fscking annoying................there are.....other,,,,,punctuation:::::::marks!!!!!!in the;;;;;;english language--------and/they~can"be"used(one)at{a}time'you((((((((know???????Also are+++++++you really''''''''so broke you)))))))can''''t afford to```````repair########your Shift key??????

I don't know what you are trying to accomplish with this kind of answers

Your previous replay was:

that is not true..... .htm, .html, .jpg,. gif,.bmp,.png,...etc..extensions...etc....are all very important in the linux file system

And now you are saying that extensions are not important, and what's important is the file permission (The same idea I have explained in my replay just right before yours)

...sure it does..... but that is because the Ubuntu Desktop handles it all for you..... as a matter of fact, your only problem may be that you have a destop setting set to hide file extensions, like they do on Winblows

As I wrote those images uses no extensions I have deleted the extensions myself, so I am not confused with anything as you think.

And finally I have no problem with anything as you thought, I am just providing a code that might benefit someone else.

As *some* people uses file extension to determine the file type which I do not consider as a good practice.

About the permission thing: Just because you *think* your files are safe it does not mean it is, consider a web server (Apache for example) that is running scripts without suexec enabled , everybody on that server will have to grant group permission to the web server in order to let it execute those scripts.

That's just one of many examples, just keep in mind that we're humans and we're prone to mistakes & you should always expect the worst thing to happen.

Finally, by adding few more checking to your code ... You are not only protecting yourself from being cracked, You are protecting other users on the shared environment you are working on. And possibly the entire server from being rooted.

Finally I am not here to discuss Linux configurations & security issues. And I will skip answering any more replays to this node.

BTW, Thanks for the MIME types url you posted as again you proved my point, take a look yourself