Man page - jl(1)

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Package: jl
apt-get install jl

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Manual

JL

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
FORMATTERS
LOG FORMATS
COPYRIGHT
SEE ALSO

NAME

jl - pretty-print JSON logs

SYNOPSIS

jl [ options... ] [ file ]

DESCRIPTION

jl is a parser and formatter for JSON logs, making machine-readable JSON logs human readable again.

jl consumes JSON logs from stdin and writes human-readable logs to stdout. To use jl , just pipe your JSON logs through it:

./my-app-executable | jl
cat app-log.json | jl

jl can read from a file:

jl my-app-log.json

jl itself doesn’t support following log files, but since it can consume from a pipe, you can use tail :

tail -F app-log.json | jl

You can page jl ’s colorised output using less with the -R flag:

jl my-app-log.json | less -R

OPTIONS

A summary of options is included below.
-color auto | yes | no

Set the color mode. The options are "auto", "yes", and "no". "auto" disables color if stdout is not a TTY (default: "auto")

-format compact | logfmt

Formatter for logs. The options are "compact" and "logfmt" (default: "compact")

-truncate [ =false ]

Whether to truncate strings in the compact formatter (default: true)

FORMATTERS

jl currently supports two formatters, with plans to make the formatters customizable.

The default is -format compact , which extracts only important fields from the JSON log, like message , timestamp , level , colorises and presents them in a easy to skim way. It drops unrecognised fields from the logs.

The other option is -format logfmt , which formats the JSON logs in a way that closely resembles logfmt This option emits all fields from each log line.

Both formatters echo non-JSON log lines as-is.

LOG FORMATS

JSON application logs tend to have some core shared fields, like level , timestamp , and message which jl tries to discover and prioritise for formatting. For now, the following formats work best with jl . For string fields other than level , only the keys matter.

Other formats can be used after preprocessing with jq .

•

Java-like:

{
"level": "error",
"timestamp": "2019-02-02 15:39:45",
"logger": "HelloWorldService",
"thread": "main",
"message": "hello world",
"exception": "java.lang.IllegalArgumentException: The world isn't here\n...stacktraces..."
}

•

Go/Logrus-like:

{
"level": "error",
"timestamp": "2019-02-02 15:39:45",
"msg": "hello world",
"error": "hello error",
"stack": "\nhello\n\thello.go\nworld\n\tworld.go"
}

COPYRIGHT

License: MIT/Expat

This manual page is based on the README document by the author. It was reformatted and adapted by Andrej Shadura <andrewsh@debian.org> for the Debian project, and is distributed under the same license as the original project.