Nicd
I’m using Port.open to execute some npm tools. This works fine on macOS and Linux but fails on Windows with the following reason:
* (ErlangError) erlang error: :eacces
erlang.erl:2080: :erlang.open_port({:spawn_executable, "/path/to/node_modules/.bin/concisecss.cmd"}, [:exit_status, :stderr_to_stdout, {:args, ["compile"]}, {:line, 1024}])
I can execute concisecss.cmd normally by opening it with Explorer, and I have checked that I have execute permission for it (this happens for every npm program, concise is here just as an example). Is it because it is a bat script? How should I run it on Windows?
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Nicd
Answering myself here with the solution. The problem was that cmd scripts can’t be spawned as executables on Windows, so I had to use
cmd.exe. I looked at the:os.cmdsources to see how Erlang does it and found the winning combination.In the end, the answer was to use
cmd.exe /c foo.cmd, but with a Windows-specific flag:hideto the Port opening call. That hides the opened cmd window and sends stdout correctly. Without the flag, the cmd window flashes on the screen and stdout never arrives back to BEAM.Here is the solution used in the end:
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Nicd
Yeah, I only found it by looking at how
:os.cmdwas implemented in the Erlang source. Later on I discovered it’s documented in the Erlang docs as:NobbZ
I can’t try it, but I think, you have to try to spawn it throuch
cmd.exeorpowershell.exeor whatever interpreter you need. Windows does not know about a concept similar to UNIX’ shebang, but has only some crippled system do determine such stuff by looking at the files ending. But this behaviour isn’t available for tools outside of windows “core” without hooping some loops.NobbZ
Google says that
cmd /c foo.cmdshould run foo.cmd without spawning a new window.Buf as far as I can remember from my erlang things I did, you will loose the access to the spawned programs stdin and -out, which is probably the mainreason for using a
Port…Last Post!
rio517
Interestingly, I ran into a similar issue on my Linux Mint dev machine. I found reinstalling dependencies and removing
_buildgot me past this.