log

Files in the top-level directory from the latest check-in

---

log
===
The logger is initialized with a configuration (table) and
the init function will return a table with functions for each
log level.

configuration
-------------
The config table contains an asignment of the log level name to a file.
The name can be a wellknown (error, info, ...) or any custom value.
There is no structure/hierarchy in log level names.
A file is defined by its path: "/var/log/file.log" (stdout|stderr)

log open modes
--------------
For different modes apply:
 | file -> pipe (|logger)
 > new file (default append)
 - open once, continuous write
 = open once, continuous write, flush

log level format
----------------
To change the date or message format for one level,
these format strings can be used before the filename:
 (d( date format )d)
 (m( message format )m) -> =d= date, =l= level, =m= message

syslog
------
The syslog module can be compiled to use logging to syslog/journald:
log_level = string.format("%d:identifier", syslog.err)
syslog levels: syslog.[emerg|alert|crit|err|warning|notice|info|debug]

configuration (tuning)
----------------------
Special values in the config table:
 ["%d"] = "!%Y/%m/%d-%H:%M:%S" -- set the date format
 ["%m"] = "=d= =l= =m=\n" -- set the log message format (d: date, l: level m: message)
 ["%s"] = syslog -- the syslog module, if used
 ["%e"] = false -- read environment variables
 if environment variables are used then
  LOG_FORMAT_MESSAGE overwrites "%m"
  LOG_FORMAT_DATE overwrites "%d"
  LOG_level overwrites "level"

logging
-------
Calling a log function can either be with just a string:
log.error("System is running 100%")
or a format string with arguments:
log.error("System is running %d%%", num_percent)

example
-------
> export LOG_err="stderr"

-- if syslog is used
local syslog = require("log_syslog")

local log_config = {
  file = "/var/log/file.log",
  pipe = "|cat",
  stdout = "(m(=d= =m=)m)(d(%s)d)=stdout",

-- if compiled with syslog
  ["%s"] = syslog,
  syslog_err  =string.format("%d:identifier", syslog.err),

-- table can contain optional fields for env and global format setup:
  ["%e"] = true,
  ["%d"] = "!%Y/%m/%d-%H:%M:%S",
  ["%m"] = "=d= =l= =m=\n",
}

local log = require("log").init(log_config)
log.err("Hello World!") -- will write to stderr (defined per env)
local name = "World"
log.file("Hello %s!", name)
log.notdefined("Hello") -- no output / no error