You can ASSIGN to an executable?!

[Amiga1992]

I can't believe in the years I have used the Amiga I never stumbled upon this, and I am not sure if it's a bug or a feature, but it turns out you can issue an ASSIGN command pointing to an executable, and when you do call that "volume" name, it launches the application.

This definitely sounds like a bug, but is it? Can anyone explain more? I just tried this on 3.1, not sure if any other versions do it.

[lesta_smsc]

I think the ASSIGN actually worked as a shortcut. Whatever you pointed it to was 'registered' as the path that would be accessed - so you could even load a image file if you wanted to!

[DisasterIncarna]

never heard of this before, interesting.

[Thomas Richter]

Originally Posted by Akira

I can't believe in the years I have used the Amiga I never stumbled upon this, and I am not sure if it's a bug or a feature, but it turns out you can issue an ASSIGN command pointing to an executable, and when you do call that "volume" name, it launches the application.

This definitely sounds like a bug, but is it? Can anyone explain more? I just tried this on 3.1, not sure if any other versions do it.

You can assign to anything you can "lock", including an arbitrary file (not only executables). I would not call this a bug, it is just a side effect of how assigns and locks work, and how they are resolved by the file system. So that is actually not an issue.



If the assign goes to a file (not a directory), opening that assign will open the file. This is because it resolves to a "lock" on the object (the file) and an empty path ("") which needs to be resolved by the file system to the object itself representing the file, the same way an empty string resolves to the current directory.


It should be even possible to "CD" into this assign, and then execute a binary through the empty string ("") through the very same mechanism.



All in all, it is just a side effect how Tripos resolves objects.

[AMIGASYSTEM]

Originally Posted by lesta_smsc

so you could even load a image file if you wanted to!

Yes indeed, with Assign you can also dismount a Volume or Floppy Device, CD etc...

[Amiga1992]

This is all so weird discovering it after 30+ years. Yeah so assign is basically a symlink.
Couldn';t anything wrong happen when a program tries to access an assign as a folder but encounters a file instead?
And how would you use a disk image this way?

[Thorham]

Originally Posted by Thomas Richter

You can assign to anything you can "lock", including an arbitrary file (not only executables). I would not call this a bug, it is just a side effect of how assigns and locks work, and how they are resolved by the file system.

Seems like they forgot to check if you specified a file or a folder. Assigning to a file makes no sense, so definitely a bug even if it can work for some things.

Originally Posted by Akira

Yeah so assign is basically a symlink.

Not exactly. Try to use 'type' on a text file you assigned to using the assign. It doesn't work.

Originally Posted by Akira

And how would you use a disk image this way?

Can't work because the OS doesn't know anything about the file system used in the disk image.

[no9]

Lol, nice catch. And since "Assign DIRS" lists those files assigned then there is a bug somewhere.

[Thomas Richter]

Originally Posted by Thorham

Seems like they forgot to check if you specified a file or a folder. Assigning to a file makes no sense, so definitely a bug even if it can work for some things.

Actually, I don't agree. This *must* work, due to the way how the file system has to operate, so I would not consider this a bug. At least, for a properly implement file system, this does not establish a problem.

Remember, the following sequence is an equivalent to OpenFromLock(lock):

 lock=Lock("myfiletooopen",SHARED_LOCK); CurrentDir(lock); /* yes, even if lock does point to a file! */ file = Open("",MODE_READ);

This looks strange, but is all according to the specs and valid code. The only thing an "assign" does is to provide a name to a lock, so it's not any different. The way how the dos.library handles an assign is that it resolves its symbolic name to a lock, and then passes the lock-name pair to the file system. The file system uses everything behind the device separator as file name, which is then just empty. Really, I know this looks bizarre, but it's just the beauty of Tripos that makes this work, and it should work.

[hooverphonique]

Originally Posted by Thomas Richter

Actually, I don't agree. This *must* work, due to the way how the file system has to operate, so I would not consider this a bug. At least, for a properly implement file system, this does not establish a problem.

Remember, the following sequence is an equivalent to OpenFromLock(lock):

 lock=Lock("myfiletooopen",SHARED_LOCK); CurrentDir(lock); /* yes, even if lock does point to a file! */ file = Open("",MODE_READ);

This looks strange, but is all according to the specs and valid code. The only thing an "assign" does is to provide a name to a lock, so it's not any different. The way how the dos.library handles an assign is that it resolves its symbolic name to a lock, and then passes the lock-name pair to the file system. The file system uses everything behind the device separator as file name, which is then just empty. Really, I know this looks bizarre, but it's just the beauty of Tripos that makes this work, and it should work.

Setting the current directory to point to a file - that's new

[Amiga1992]

I still fail to see how this is not a bug since any other use but a directory seems to be problematic.

[Thorham]

Originally Posted by Thomas Richter

Really, I know this looks bizarre, but it's just the beauty of Tripos that makes this work, and it should work.

At the OS level, perhaps, but I see no reason why it should work in the console. You can't assign to a file and cd to it, for example. You can't type text files. Seems better to disable it in the console assign command (not talking about the OS level).

[AMIGASYSTEM]

Originally Posted by no9

Lol, nice catch. And since "Assign DIRS" lists those files assigned then there is a bug somewhere.

There is no need to Write "Assign DIRS", to see all the assignments in the system you only need to write "ASSIGN"

Assign I would say is the most representative command of the Amiga system.

Years ago when I was burning PC-Windows Games and Applications to CD, if I made a mistake in label name, you could trash the CD, instead you would just have to have the Assign command on PC to use that CD normally.

Always another Amiga peculiarity, although many people do not know it, there is an Amiga Device that allows you to Edit, Rename, delete files from the CD "virtually", very convenient when in the CD you do not want to show folders with viruses, corrupted files etc..

[Thorham]

Originally Posted by AMIGASYSTEM

Years ago when I was burning PC-Windows Games and Applications to CD, if I made a mistake in label name, you could trash the CD, instead you would just have to have the Assign command on PC to use that CD normally.

CD-RW

[AMIGASYSTEM]

Originally Posted by Thorham

CD-RW

No !!! I'm talking about a "Real" CD-RW Burner, but a software "AMiGA" that allows you to change the data of a CD "Virtually" !!!!

All changed or deleted data is added on a folder called "Data", if you delete the folder "DATA" the CD will be visible as it was in original !!!!

Of course the CD with a normal Device will be seen in its entirety, only the mentioned Device can see and use the changes !!!

If I was not clear, I will make a comprehensive video !!!

[Thorham]

Originally Posted by AMIGASYSTEM

If I was not clear, I will make a comprehensive video !!!

I meant burning the CD and then tossing the CD because it went wrong, not the device.

[no9]

Originally Posted by AMIGASYSTEM

There is no need to Write "Assign DIRS", to see all the assignments in the system you only need to write "ASSIGN"

That's not the point. When you deliberately specify the parameter that supposedly lists directories it should print only them. Otherwise it is misleading and wrong.

If you don't specify any parameters the assign command can print whatever it wants, even a random poems. That's why it is a bug.

[Karlos]

That's interesting. Something (somewhat unrelated but equally odd ) that I used to do that worked for a lot of applications was to make their directory icon a project and then make the default tool for opening it the actual application inside. Probably not wise, but was inspired by the way application drawers in RiscOS worked.

[paul1981]

@Akira

Sounds like one of those Mandela thingamabobs. Never heard of it in my life! Then again, I was just as surprised a couple of years ago when I discovered ASL had a delete function in the menu, and that the 'Update All' function in the Workbench menu actually worked as I swear it never used to. I'm talking 3.0 here in both cases. Been using it for 30 years almost.

@Karlos

I wonder if that is a feature and that's where RiscOS nicked it from in the first place? (Tripos).