:mod:!syslog --- Unix syslog library routines

.. module:: syslog :synopsis: An interface to the Unix syslog library routines.

This module provides an interface to the Unix syslog library routines. Refer to the Unix manual pages for a detailed description of the syslog facility.

.. availability:: Unix, not WASI, not iOS.

This module wraps the system syslog family of routines. A pure Python library that can speak to a syslog server is available in the :mod:logging.handlers module as :class:~logging.handlers.SysLogHandler.

The module defines the following functions:

.. function:: syslog(message) syslog(priority, message)

Send the string message to the system logger. A trailing newline is added if necessary. Each message is tagged with a priority composed of a facility and a level. The optional priority argument, which defaults to :const:LOG_INFO, determines the message priority. If the facility is not encoded in priority using logical-or (LOG_INFO | LOG_USER), the value given in the :func:openlog call is used.

If :func:openlog has not been called prior to the call to :func:syslog, :func:openlog will be called with no arguments.

.. audit-event:: syslog.syslog priority,message syslog.syslog

.. versionchanged:: 3.2 In previous versions, :func:openlog would not be called automatically if it wasn't called prior to the call to :func:syslog, deferring to the syslog implementation to call openlog().

.. versionchanged:: 3.12 This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) :func:openlog must be called in the main interpreter before :func:syslog may be used in a subinterpreter. Otherwise it will raise :exc:RuntimeError.

.. function:: openlog([ident[, logoption[, facility]]])

Logging options of subsequent :func:syslog calls can be set by calling :func:openlog. :func:syslog will call :func:openlog with no arguments if the log is not currently open.

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. The optional logoption keyword argument (default is 0) is a bit field -- see below for possible values to combine. The optional facility keyword argument (default is :const:LOG_USER) sets the default facility for messages which do not have a facility explicitly encoded.

.. audit-event:: syslog.openlog ident,logoption,facility syslog.openlog

.. versionchanged:: 3.2 In previous versions, keyword arguments were not allowed, and ident was required.

.. versionchanged:: 3.12 This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) This may only be called in the main interpreter. It will raise :exc:RuntimeError if called in a subinterpreter.

.. function:: closelog()

Reset the syslog module values and call the system library closelog().

This causes the module to behave as it does when initially imported. For example, :func:openlog will be called on the first :func:syslog call (if :func:openlog hasn't already been called), and ident and other :func:openlog parameters are reset to defaults.

.. audit-event:: syslog.closelog "" syslog.closelog

.. versionchanged:: 3.12 This function is restricted in subinterpreters. (Only code that runs in multiple interpreters is affected and the restriction is not relevant for most users.) This may only be called in the main interpreter. It will raise :exc:RuntimeError if called in a subinterpreter.

.. function:: setlogmask(maskpri)

Set the priority mask to maskpri and return the previous mask value. Calls to :func:syslog with a priority level not set in maskpri are ignored. The default is to log all priorities. The function LOG_MASK(pri) calculates the mask for the individual priority pri. The function LOG_UPTO(pri) calculates the mask for all priorities up to and including pri.

.. audit-event:: syslog.setlogmask maskpri syslog.setlogmask

The module defines the following constants:

.. data:: LOG_EMERG LOG_ALERT LOG_CRIT LOG_ERR LOG_WARNING LOG_NOTICE LOG_INFO LOG_DEBUG

Priority levels (high to low).

.. data:: LOG_AUTH LOG_AUTHPRIV LOG_CRON LOG_DAEMON LOG_FTP LOG_INSTALL LOG_KERN LOG_LAUNCHD LOG_LPR LOG_MAIL LOG_NETINFO LOG_NEWS LOG_RAS LOG_REMOTEAUTH LOG_SYSLOG LOG_USER LOG_UUCP LOG_LOCAL0 LOG_LOCAL1 LOG_LOCAL2 LOG_LOCAL3 LOG_LOCAL4 LOG_LOCAL5 LOG_LOCAL6 LOG_LOCAL7

Facilities, depending on availability in <syslog.h> for :const:LOG_AUTHPRIV, :const:LOG_FTP, :const:LOG_NETINFO, :const:LOG_REMOTEAUTH, :const:LOG_INSTALL and :const:LOG_RAS.

.. versionchanged:: 3.13 Added :const:LOG_FTP, :const:LOG_NETINFO, :const:LOG_REMOTEAUTH, :const:LOG_INSTALL, :const:LOG_RAS, and :const:LOG_LAUNCHD.

.. data:: LOG_PID LOG_CONS LOG_NDELAY LOG_ODELAY LOG_NOWAIT LOG_PERROR

Log options, depending on availability in <syslog.h> for :const:LOG_ODELAY, :const:LOG_NOWAIT and :const:LOG_PERROR.

Examples

Simple example

A simple set of examples::

   import syslog

   syslog.syslog('Processing started')
   if error:
       syslog.syslog(syslog.LOG_ERR, 'Processing started')

An example of setting some log options, these would include the process ID in
logged messages, and write the messages to the destination facility used for
mail logging::

   syslog.openlog(logoption=syslog.LOG_PID, facility=syslog.LOG_MAIL)
   syslog.syslog('E-mail processing initiated...')