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/>

                                                   2023-08-24                                              JL(1)