# `syslog` — 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 Emscripten, not WASI.

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`.

The module defines the following functions:

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.

  Raises an auditing event `syslog.syslog` with arguments `priority`, `message`.

  Changed in version 3.2: In previous versions, `openlog()` would not be called automatically if it wasn’t called prior to the call to `syslog()`, deferring to the syslog implementation to call `openlog()`.

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.

  Raises an auditing event `syslog.openlog` with arguments `ident`, `logoption`, `facility`.

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

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.

  Raises an auditing event `syslog.closelog` with no arguments.

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.

  Raises an auditing event `syslog.setlogmask` with argument `maskpri`.

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`.

## 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...')