youtube-dl youtube.com/user/<ytuser> -j | grep -m 1 -Po '(?<="uploader_id": ")[^"]*' fails

[sapphonie]

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Add -v flag to your command line you run youtube-dl with, copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

bash shell, btw

$ youtube-dl youtube.com/user/supdawg444 -v -j | grep -m 1 -Po '(?<="uploader_id": ")[^"]*'
[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'youtube.com/user/supdawg444', u'-v', u'-j']
[debug] Encodings: locale UTF-8, fs UTF-8, out None, pref UTF-8
[debug] youtube-dl version 2016.04.13
[debug] Python version 2.7.10 - Linux-4.2.0-35-generic-x86_64-with-Ubuntu-15.10-wily
[debug] exe versions: avconv 2.7.6-0ubuntu0.15.10.1, avprobe 2.7.6-0ubuntu0.15.10.1, ffmpeg 2.7.6-0ubuntu0.15.10.1, ffprobe 2.7.6-0ubuntu0.15.10.1, rtmpdump 2.4
[debug] Proxy map: {}
WARNING: The url doesn't specify the protocol, trying with http
supdawg444
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/local/bin/youtube-dl/__main__.py", line 19, in <module>
  File "/usr/local/bin/youtube-dl/youtube_dl/__init__.py", line 419, in main
  File "/usr/local/bin/youtube-dl/youtube_dl/__init__.py", line 409, in _real_main
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1730, in download
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 682, in extract_info
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 734, in process_ie_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 682, in extract_info
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 734, in process_ie_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 682, in extract_info
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 842, in process_ie_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 734, in process_ie_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 682, in extract_info
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 727, in process_ie_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1376, in process_video_result
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1479, in process_info
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 442, in to_stdout
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 431, in _write_string
  File "/usr/local/bin/youtube-dl/youtube_dl/utils.py", line 1167, in write_string
IOError: [Errno 32] Broken pipe
...
<end of log>

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Description of your issue, suggested solution and other information

No idea. Seems like running grep on some json output fails, for some reason. I'm just trying to come up with a regex expression to grep on the JSON output.

So far I can do

youtube-dl youtube.com/user/<user> -v -j | grep -Po '(?<="uploader_id": ")[^"]* 

and get the uploader_id, but it outputs it every time it finds a new video, so I end up with the uploader_id duplicated for however many videos the youtube channel has.

That's what the -m 1 in the grep command was for, but it failed. No idea why.

[dstftw]

You should not grep on JSON use jq instead.
-m 1 fails since grep stops reading from stdin after the first match while youtube-dl continues to write into pipe on each new video. Limit processing to just one video if you don't need to process all --playlist-end 1.

[sapphonie]

I ended up doing --playlist-items 1:

https://github.com/TheSqrtMinus1/download-youtube-channel-hq