The glu.log module

The glu.log module provides structured logging from Lua. It uses the same logging backend as glu itself — messages appear in the same format and are controlled by the --loglevel flag.

local log = require("glu.log")

Functions

Function	Level	Description
`debug(msg, ...)`	debug	Verbose output for development
`info(msg, ...)`	info	Normal operational messages
`warn(msg, ...)`	warn	Potential problems
`error(msg, ...)`	error	Errors that need attention

Usage

Each function takes a message string followed by optional key-value pairs:

local log = require("glu.log")

log.info("Processing started", "file", "report.md")
log.warn("Missing field", "field", "author", "page", 3)
log.debug("Computed value", "result", 42)

Output (with --loglevel info):

·   Processing started (file=report.md)
W: Missing field (field=author,page=3)

The debug message is suppressed because the log level is info. To see debug messages:

glu --loglevel debug document.md

Log levels

The --loglevel flag controls which messages are visible:

Level	Shows
`debug`	debug, info, warn, error
`info`	info, warn, error (default)
`warn`	warn, error
`error`	error only

Lua log messages and glu’s internal log messages share the same level — setting --loglevel debug shows both your messages and glu’s internal diagnostics.

Example: logging in callbacks

local frontend = require("glu.frontend")
local log = require("glu.log")

frontend.add_callback("document_start", "log_start", function()
    log.info("Document processing started")
end)

frontend.add_callback("pre_shipout", "log_page", function(doc, page, pagenum)
    log.debug("Shipping page", "page", pagenum)
end)

frontend.add_callback("document_end", "log_end", function()
    log.info("Document finished", "pages", _aux._pages)
end)

json module