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I'm a Python newbie, and the following code wrote the following messages to /var/log/syslog

May 8 22:14:22.531833 almach <info>./test.txt: HELLO 01 May 8 22:14:22.531853 almach <info>./test.txt: HELLO 02 May 8 22:14:22.531860 almach <info>./test.txt: HELLO 03

So, why

  1. Messages were written to /var/log/syslog and not ./test.txt?

  2. setlogmask(0) was ineffective, and message "HELLO 02" was written to syslog?

Also, I tested the code in a Linux machine that had demon rsyslogd running, and it might have affected my code somehow.

from syslog import syslog, setlogmask, LOG_INFO, openlog openlog('./test.txt') syslog(LOG_INFO, "HELLO 01") setlogmask(0) syslog(LOG_INFO, "HELLO 02") setlogmask(255) syslog(LOG_INFO, "HELLO 03")
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    You cannot setlogmask(0). The mask must be a bitwise combination of the symbolic constants. Commented May 8, 2019 at 22:44

2 Answers 2

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2

You need to use LOG_MASK(0) to avoid writing HELLO 02 and remember previous value of mask to restore it before writing HELLO 03:

from syslog import syslog, setlogmask, LOG_INFO, LOG_MASK, openlog openlog('./test.txt') syslog(LOG_INFO, "HELLO 01") mask = setlogmask(LOG_MASK(0)) syslog(LOG_INFO, "HELLO 02") setlogmask(mask) syslog(LOG_INFO, "HELLO 03")

Result in /var/log/syslog:

May 9 01:49:39 sanyash-ub16 ./test.txt: HELLO 01 May 9 01:49:39 sanyash-ub16 ./test.txt: HELLO 03
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From syslog.openlog manual:

The optional ident keyword argument is a string which is prepended to every message, and defaults to sys.argv[0] with leading path components stripped

To save logs in a separate file, use logging.handlers.SysLogHandler: How to configure logging to syslog in Python?

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