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

       Copyright (C) 2019-2023 Yunchi Luo

       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.

SEE ALSO

       jq(1), <https://blog.codeship.com/logfmt-a-log-format-thats-easy-to-read-and-write/>

                                            2024-01-23                                      JL(1)