Windows named pipe output prompts to overwrite

[James]

Summary of the bug: Using Named Pipe syntax on Windows results in an interactive prompt to overwrite the target file. Named pipes aren't really files, they're more like a listening server socket, so this prompt makes no sense.

How to reproduce: First, listen to a new named pipe. This is outside the scope of this issue, but ​this StackOverflow answer shows how to listen via NodeJS, for example. Say your pipe is \\.\pipe\SomePipeName, the relevant command would be

% ffmpeg -i infile.ts -codec copy -f data "\\.\pipe\SomePipeName"
ffmpeg version 3.4 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
...
File '\\.\pipe\SomePipeName' already exists. Overwrite ? [y/N]

This isn't an error condition and shouldn't result in any kind of prompt. If nobody is listening on that pipe name, which is in fact an error, the message is instead "no such file or directory". This sort of makes sense but it would be more accurate to say that the pipe couldn't connect.

[Carl Eugen Hoyos]

Please test current FFmpeg git head and provide the command line you tested together with the complete, uncut console output to make this a valid ticket.
If you know how to distinguish between file and pipe on Windows please consider sending a patch - made with git format-patch - to the development mailing list.

[James]

OK, I grabbed the nightly build from ​here, below is the uncut console output -- until the prompt is answered, which does result in the output being piped successfully.

> ffmpeg.exe -i "sample.ts" -map 0:1 -codec copy -f data "\\.\pipe\klvin"
ffmpeg version N-91473-gc5329d64b1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 7.3.1 (GCC) 20180710
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth
  libavutil      56. 18.102 / 56. 18.102
  libavcodec     58. 21.105 / 58. 21.105
  libavformat    58. 17.101 / 58. 17.101
  libavdevice    58.  4.101 / 58.  4.101
  libavfilter     7. 25.100 /  7. 25.100
  libswscale      5.  2.100 /  5.  2.100
  libswresample   3.  2.100 /  3.  2.100
  libpostproc    55.  2.100 / 55.  2.100
[mpegts @ 0000024c14d3a200] start time for stream 1 is not set in estimate_timings_from_pts
Input #0, mpegts, from 'sample.ts':
  Duration: 00:03:14.88, start: 10.000000, bitrate: 4187 kb/s
  Program 1
    Stream #0:0[0x1e1]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1280x720, 60 fps, 60 tbr, 90k tbn, 180k tbc
    Stream #0:1[0x1f1]: Data: klv (KLVA / 0x41564C4B)
File '\\.\pipe\klvin' already exists. Overwrite ? [y/N]