File exists check

OwenD

It would be good if we could get the result of whether a file exists in G Code.
For example could M36 be changed to return an error code 1 or 2 if the file isn't found?
At present it returns the error state as part of the JSON response but returns and error state of zero even if the file isn't found.

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.