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Merged
merged 3 commits into from
Sep 23, 2024
Merged

cli: add devnull fallback for missing stdout fd #6197

merged 3 commits into from
Sep 23, 2024

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bastimeyer
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Follow-up of #6142

This fixes the case where sys.stdout is None, when the Python process doesn't have the stdout file descriptor (fd1). This can be forced in BASH for example, by appending >&-.

import pathlib,os,sys
pid = str(os.getpid())
fd1 = pathlib.Path("/proc", pid, "fd", "1")
sys.stderr.write(f"{pid=}\n{sys.stdout is None=}\n{fd1.readlink() if fd1.exists() else None=}\n")
$ python <<< "${CODE}"
pid='318408'
sys.stdout is None=False
fd1.readlink() if fd1.exists() else None=PosixPath('/dev/pts/2')
$ python <<< "${CODE}" >&-
pid='318428'
sys.stdout is None=True
fd1.readlink() if fd1.exists() else None=None

Currently on master, this results in an AttributeError, as the streamlink_cli.compat module assigns its stdout attribute to sys.stdout.buffer, the binary output stream used for writing stream content to stdout (e.g. --stdout).

So when fd1 is missing and sys.stdout is None, we need a fallback stream. Simply use a devnull output stream in this case (and close it on exit).

When stdout is missing, the logging stream and console output stream will automatically be stderr.

master

$ streamlink >&-
Traceback (most recent call last):
  File "/home/basti/venv/streamlink-312/bin/streamlink", line 5, in <module>
    from streamlink_cli.main import main
  File "/home/basti/repos/streamlink/src/streamlink_cli/main.py", line 25, in <module>
    from streamlink_cli.argparser import ArgumentParser, build_parser, setup_session_options
  File "/home/basti/repos/streamlink/src/streamlink_cli/argparser.py", line 13, in <module>
    from streamlink_cli.constants import STREAM_PASSTHROUGH
  File "/home/basti/repos/streamlink/src/streamlink_cli/constants.py", line 7, in <module>
    from streamlink_cli.compat import DeprecatedPath
  File "/home/basti/repos/streamlink/src/streamlink_cli/compat.py", line 6, in <module>
    stdout: BinaryIO = sys.stdout.buffer
                       ^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'buffer'

PR

$ streamlink >&-
usage: streamlink [OPTIONS] <URL> [STREAM]

Use -h/--help to see the available options or read the manual at https://streamlink.github.io

$ streamlink --stdout httpstream://file:///dev/zero best >&-
[cli][info] Found matching plugin http for URL httpstream://file:///dev/zero
[cli][info] Available streams: live (worst, best)
[cli][info] Opening stream: live (http)
^C[cli][info] Stream ended
Interrupted! Exiting...
[cli][info] Closing currently open stream...

Removing stderr as well is currently unsupported, and the process will stop because of a failure of the logging / console output setup, which falls back to stderr if stdout is None. Maybe I'll have a look at this later, too.

$ streamlink >&- 2>&-; echo $?
1

@bastimeyer bastimeyer force-pushed the cli/missing-stdout-fallback branch from 3cf5eb0 to 819b581 Compare September 23, 2024 22:54
@bastimeyer bastimeyer force-pushed the cli/missing-stdout-fallback branch from 819b581 to 633aa8f Compare September 23, 2024 23:09
@bastimeyer
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No stdout/stderr

$ streamlink >&- 2>&-; echo $?
0

$ streamlink -l debug --logfile /tmp/log >&- 2>&- && cat /tmp/log
[cli][debug] OS:         Linux-6.11.0-1-git-x86_64-with-glibc2.40
[cli][debug] Python:     3.12.6
[cli][debug] OpenSSL:    OpenSSL 3.3.2 3 Sep 2024
[cli][debug] Streamlink: 6.10.0+34.g633aa8f4
[cli][debug] Dependencies:
[cli][debug]  certifi: 2024.8.30
[cli][debug]  isodate: 0.6.1
[cli][debug]  lxml: 5.3.0
[cli][debug]  pycountry: 24.6.1
[cli][debug]  pycryptodome: 3.20.0
[cli][debug]  PySocks: 1.7.1
[cli][debug]  requests: 2.32.3
[cli][debug]  trio: 0.26.2
[cli][debug]  trio-websocket: 0.12.0.dev0
[cli][debug]  typing-extensions: 4.12.2
[cli][debug]  urllib3: 2.2.3
[cli][debug]  websocket-client: 1.8.0
[cli][debug] Arguments:
[cli][debug]  --loglevel=debug
[cli][debug]  --logfile=/tmp/log
[cli][debug]  --player=/usr/bin/mpv
[cli][debug]  --webbrowser-headless=True
usage: streamlink [OPTIONS] <URL> [STREAM]

Use -h/--help to see the available options or read the manual at https://streamlink.github.io

$ streamlink -o /tmp/foo -f --hls-duration=10 URL best >&- 2>&- \
  && ffprobe -v error -of json -show_streams /tmp/foo | jq -r ".streams[0].duration"
9.984567

@bastimeyer bastimeyer marked this pull request as ready for review September 23, 2024 23:13
@bastimeyer bastimeyer merged commit 65d49fb into streamlink:master Sep 23, 2024
25 checks passed
@bastimeyer bastimeyer deleted the cli/missing-stdout-fallback branch September 23, 2024 23:14
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@bastimeyer