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I have a custom service and have explicitly called for all stdout & stderr to be sent to syslog in the config file, however only some of the output appears in both syslog and the journal (they are consistent).

I my desperation I have done the following in the service files:

StandardOutput=syslog+console
StandardError=syslog+console

The service is a python script and I write to stdout using the print statement. These items seem to be lost to the ether, while other command outputs write correctly both to syslog and journald. If I run the script interactively everything appears in stdout as expected.

What is lacking in my knowledge?

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1 Answer 1

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JdeBP's comment was the correct solution:

Systemd Python service not sending all output to syslog

The solution was to add the -u option to the interpreter to make standard streams send their output unbuffered.

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  • For me adding -u wasn't a good option. Another way to do it is to call sys.stdout.flush() whenever stdout needs to be written. Jan 21, 2021 at 7:07
  • For what it's worth, you can also set PYTHONUNBUFFERED to a non-empty string which is equivalent to specifying the -u option in Python2 and Python3 (Source: docs.python.org/3/using/cmdline.html#envvar-PYTHONUNBUFFERED)
    – M1GEO
    Dec 1, 2021 at 13:45
  • 1
    you can set a shebang like #!/usr/bin/python3 -u on your python script, set exec permissions and call it directly from your .service
    – iambr
    Jan 12 at 13:49

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