Prettylog

Command line tool that displays JSON logs in a human-friendly format.

Installation

Go 1.17+:

go install github.com/globocom/prettylog@latest

Go 1.16 or older:

curl https://github.com/globocom/prettylog/raw/master/install.sh | sh

Prettylog will be installed to $GOPATH/bin. Make sure to add it to your PATH so you can run prettylog anywhere.

How it works

Prettylog parses log messages that contain an arbitrary number of fields and generates a nice output in the following format:

<TIMESTAMP> <LOGGER> <CALLER> <LEVEL> <MESSAGE> <FIELD1>=<VALUE> <FIELD2>=<VALUE> ...

Non-existent fields will be ignored and messages not encoded as JSON will be printed as is.

Usage

Simply pipe the stdout of an application that outputs structured log messages into prettylog:

app | prettylog

You might need to redirect stderr to stdout if the application doesn't log to the standard output:

app 2>&1 | prettylog

Configuration

You can configure how Prettylog works by creating a .prettylog.yml file either locally (per directory) or globally (in $HOME):

timestamp:
  key:     <string>
  visible: <bool>
  color:   <list of int>
  format:  <string>

logger:
  key:     <string>
  visible: <bool>
  padding: <int>
  color:   <list of int>

caller:
  key:     <string>
  visible: <bool>
  padding: <int>
  color:   <list of int>

level:
  key:     <string>
  visible: <bool>
  padding: <int>
  colors:
    debug: <list of int>
    info:  <list of int>
    warn:  <list of int>
    error: <list of int>
    fatal: <list of int>

message:
  key:     <string>
  padding: <int>
  color:   <list of int>

Each field has its own key and the following properties are available:

Name	Description
key	Field name.
visible	Flag indicating whether the field will be printed.
padding	Number of whitespaces that will be added to the right of the field.
color/colors	Color attributes. Up to 3 values can be used (fg, bg and effects). More information here.
format	(timestamp field only) Layout that will be used to print timestamp values. It must follow the rules of the time package.

Using with other tools

Prettylog can be used along with other command line tools. Just make sure no buffer is enabled. For instance, grep has a --line-buffered flag:

app | grep --line-buffered -v debug | prettylog

If the tool you want to use buffers its output and does not offer such a flag, you can try stdbuff.