File exists check

[dc42]

I've added this to the work list.

[DonStauffer]

@dc42 Has it been decided what firmware version this will be in? Thanks!

[Phaedrux]

@donstauffer I believe it will be in 3.3

exists name -> bool Yields true if 'name' is a valid variable or object model element name and is not null (available in RRF 3.3beta3 and later). Especially useful for testing whether a particular parameter has been provided when a file macro was called.

https://duet3d.dozuki.com/Wiki/GCode_Meta_Commands#Section_Functions

[DonStauffer]

@phaedrux This is about files, not variables.

[Phaedrux]

@donstauffer ah, my mistake.

[DonStauffer]

@phaedrux I found a very awkward workaround: M471 is the only code I know of which returns a result that tells you something about the existence of a file. Unfortunately, it does that when potentially deleting the file in question. I didn't want that, so I had to set up a system of dummy "semaphor" files created in parallel with the file I was interested in, which fortunately my macros created, so it could keep the semaphors consistent with the actual file status.

But all that turned what would have been about a half page of code with a file exists capability into about 2 pages.

[Phaedrux]

@dc42 would have to comment on whether it's been implemented yet for sure.

[OwenD]

As a work around you can use M38.

M38: Compute SHA1 hash of target file

Example:

M38 gcodes/myfile.g

Used to compute a hash of a file on the SD card and returns a hexadecimal string which is the SHA1 of the file. If the file cannot be found, then the string "Cannot find file" is returned instead.

[DonStauffer]

@owend How can my GCode use the string returned by M38? For example, how could I use it in a conditional? How do I suppress the spurious error message which displays in the console and as a pop-up in the web interface?

[OwenD]

@donstauffer
You can't suppress the error message.
You don't exactly use the string. It's more a case of checking the result.
A result code of zero means I it's found and RRF was able to create a hash.
A result of 2 means the files wasn't found.
A result of 1 means the call to M38 returned a warning but I'm not sure of what conditions might return that result.

It's not very elegant but it's the best we have for now.

M38 "gcodes/my file.g"
if result = 2
      echo "file not found"
elif result  = 1
    echo "M38 call failed"
elif result = 0
    echo "file exists"

[mher]

@dc42 Is there any news about this. It would be really nice to check if a file exists or not.

[dc42]

@mher a new function fileexists(name) is already implemented in the RRF 3.5 source code.