Unix syslog 库例程
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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.

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

这个模块定义了以下函数：

syslog.syslog(message)
syslog.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 "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
   "openlog()" call is used.

   If "openlog()" has not been called prior to the call to "syslog()",
   "openlog()" will be called with no arguments.

syslog.openlog([ident[, logoption[, facility]]])

   Logging options of subsequent "syslog()" calls can be set by
   calling "openlog()".  "syslog()" will call "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 "LOG_USER") sets the default facility for messages
   which do not have a facility explicitly encoded.

   在 3.2 版更改: In previous versions, keyword arguments were not
   allowed, and *ident* was required.  The default for *ident* was
   dependent on the system libraries, and often was "python" instead
   of the name of the Python program file.

syslog.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, "openlog()" will be called on the first
   "syslog()" call (if "openlog()" hasn't already been called), and
   *ident* and other "openlog()" parameters are reset to defaults.

syslog.setlogmask(maskpri)

   Set the priority mask to *maskpri* and return the previous mask
   value.  Calls to "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*.

The module defines the following constants:

Priority levels (high to low):
   "LOG_EMERG", "LOG_ALERT", "LOG_CRIT", "LOG_ERR", "LOG_WARNING",
   "LOG_NOTICE", "LOG_INFO", "LOG_DEBUG".

Facilities:
   "LOG_KERN", "LOG_USER", "LOG_MAIL", "LOG_DAEMON", "LOG_AUTH",
   "LOG_LPR", "LOG_NEWS", "LOG_UUCP", "LOG_CRON", "LOG_SYSLOG",
   "LOG_LOCAL0" to "LOG_LOCAL7", and, if defined in "<syslog.h>",
   "LOG_AUTHPRIV".

Log options:
   "LOG_PID", "LOG_CONS", "LOG_NDELAY", and, if defined in
   "<syslog.h>", "LOG_ODELAY", "LOG_NOWAIT", and "LOG_PERROR".


示例
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Simple example
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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...')
