ifzz / lua-syslog

Syslog module for Lua

lua-syslog

Table of Contents

• Usage
• Functions
  • logger:open(ident[, option[, facility]])
  • logger:strerror()
  • logger:log(level[, facility], message)
  • logger:close()
  • logger:setmask{emerg, alert, crit, err, warning, notice, info, debug}

A syslog binding for Lua 5.3.

Usage

local logger = require('syslog')

Functions

logger:open(ident[, option[, facility]])

:open opens a connection to the system logger for a program.

ident is the string prepended to every message, and is typically set to the program name.

The option argument specifies flags which control the operation of :open and subsequent calls to :log.

The option argument is a bitwise OR of any of these: ^[1]

logger.option.cons

Write directly to system console if there is an error while sending to system logger.

logger.option.ndelay

Open the connection immediately (normally, the connection is opened when the first message is logged).

logger.option.nowait

Don’t wait for child processes that may have been created while logging the message. (The GNU C library does not create a child process, so this option has no effect on Linux.)

logger.option.odelay

The converse of logger.option.ndelay; opening of the connection is delayed until :log is called. (This is the default, and need not be specified.)

logger.option.perror

Print to stderr as well.

Since this is a GNU extension, it it set to 0 on systems that do not support it. (Basically, it is silently ignored.)

logger.option.pid

Include PID with each message.

The facility argument is used to specify what type of program is logging the message. This lets the configuration file specify that messages from different facilities will be handled differently.

"auth"	security/authorization messages
"authpriv"	security/authorization messages (private)
"cron"	clock daemon (cron and at)
"daemon"	system daemons without separate facility value
"ftp"	ftp daemon
"kern"	kernel messages (these can’t be generated from user processes)
"local0" through "local7"	reserved for local use
"lpr"	line printer subsystem
"mail"	mail subsystem
"news"	USENET news subsystem [2]
"syslog"	messages generated internally by syslogd
"user" (default)	generic user-level messages
"uucp"	UUCP subsystem

The use of :open is optional on many systems.

logger:strerror()

Returns a string describing the most recent error.

lua_pushstring(L, strerror(errno));

logger:log(level[, facility], message)

:log generates a log message, which will be distributed by syslogd.

The level argument determines the importance of the message. The levels are, in order of decreasing importance:

"emerg"	system is unusable
"alert"	action must be taken immediately
"crit"	critical conditions
"err"	error conditions
"warning"	warning conditions
"notice"	normal, but significant, condition
"info"	informational message
"debug"	debug-level message

The optional facility argument is the same as for :open.

The message argument is the error message. A trailing newline may be added if needed.

logger:close()

Closes the descriptor being used to write to the system logger. The use of :close is optional.

logger:setmask{emerg, alert, crit, err, warning, notice, info, debug}

Restrict logging to the specified levels only.

This function takes one argument, which is a table containing the desired levels.

Here, let me just give you an example:

Only log emerg, alert, crit, and err

logger:setmask{
    emerg = true,
    alert = true,
    crit  = true,
    err   = true,
}

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1. By the way, Lua 5.3 has a bitwise OR operator now! (It’s the same as in C)

2. Perhaps system logging facilities should not have a hard-coded list of subsystems…​