can't make example from docopt.org work

[dselivanov]

Newbie here. Here is example from http://docopt.org/:

Naval Fate.

Usage:
  naval_fate ship new <name>...
  naval_fate ship <name> move <x> <y> [--speed=<kn>]
  naval_fate ship shoot <x> <y>
  naval_fate mine (set|remove) <x> <y> [--moored|--drifting]
  naval_fate -h | --help
  naval_fate --version

Options:
  -h --help     Show this screen.
  --version     Show version.
  --speed=<kn>  Speed in knots [default: 10].
  --moored      Moored (anchored) mine.
  --drifting    Drifting mine.

Trying to make it work from R:

library(docopt)
doc ='
Naval Fate.

Usage:
  naval_fate ship new <name>...
  naval_fate ship <name> move <x> <y> [--speed=<kn>]
  naval_fate ship shoot <x> <y>
  naval_fate mine (set|remove) <x> <y> [--moored|--drifting]
  naval_fate -h | --help
  naval_fate --version

Options:
  -h --help     Show this screen.
  --version     Show version.
  --speed=<kn>  Speed in knots [default: 10].
  --moored      Moored (anchored) mine.
  --drifting    Drifting mine.
'
opt = docopt(doc)

Getting uninformative error:

Error: 
 usage: naval_fate ship new <name>...
  
 usage: naval_fate ship <name> move <x> <y> [--speed=<kn>]
  
 usage: naval_fate ship shoot <x> <y>
  
 usage: naval_fate mine (set|remove) <x> <y> [--moored|--drifting]
  
 usage: naval_fate -h | --help
  
 usage: naval_fate --version

[edwindj]

Thanks for reporting, I'll look into it tomorrow!

Best

[t-kalinowski]

I think the error you're seeing is because you're using it in a context where the command line args to the R session are not a valid "usage". To simulate command line args, try

docopt(doc, "-h")
# or
docopt(doc, c("ship",  "new",  "Boaty McBoatface"))

[stucash]

I think the error you're seeing is because you're using it in a context where the command line args to the R session are not a valid "usage". To simulate command line args, try

docopt(doc, "-h")
# or
docopt(doc, c("ship",  "new",  "Boaty McBoatface"))

I actually tried to put it to test in real command-line environment. i.e. I have a rscript file (where we have that typical line of #!/usr/bin/Rscript, with correct permission (in linux sudo chmod +755). I ran this file from my terminal, and I got the same error.

[stucash]

Ok so I think I somehow get the idea now. We do need to run the actual script in a real terminal to get it to work correctly but that is a little bit implicit in documentation.... (too implicit to actually see it anywhere.... :P )

Firstly, it is right if you run your script from RStudio (for example) you'll have to provide dummy values for docopt to understand you are simulating the real command-line environment and to feed you back with correct simulated output.

The same logic applies in terminal experiment as well. The example on the front page is supposed to be run with actual input value for each argument for docopt to understand.

i.e. let's call our front-page example file 'test.R' and it has correct permission, ./test.R ship new something ./test.R ship something move 10 50 --speed=20

to test incorrect usage as suggested, ./test.R ship mine

all output on terminal should match the results demonstrated on the front page.