Logan

A simple CLI tool to make working with log files easier.

Usage

Logan supports multiple "processors" which determines the output format. It can be used to print out lines with different colors, define "events" to capture lines between a "start" and an "end" or simply filter the output (grep). Logan can be used with CLI commands or a config file. Using it with CLI commands are simpler but limited to a single processor. The following processors are available right now:

Coloring lines

You can print out lines with different colors with the colorize command:

$ logan example.log colorize -p "INFO" 28 -p "WARN" 24 -p "ERROR" 88

Where the first parameter is a regex pattern and the second is a color. You can also define a prefix that will be prepended to every pattern with the -P or --prefix argument:

$ logan example.log colorize -P "[\d]{4}-[\d]{2}-[\d]{2} [\d]{2}:[\d]{2}:[\d]{2} " -p "INFO" 28 -p "WARN" 24 -p "ERROR" 88

Note

The color parameter refers to a palette index of your terminal app. It will be possible to define RGB colors in a future release. You have to check out your terminal's color palette to know which index is which color.

Events

You can define events with the events command. It takes a start and end pattern that will define an event. E.g. if you want to check out mouse clicks in a log file you can use the following:

$ logan example.log events -P "[\d]{4}-[\d]{2}-[\d]{2} [\d]{2}:[\d]{2}:[\d]{2} INFO " -c 28 "Mouse left down" "Mouse left up"

Which will print all lines between the occurence (including both ends) of lines containing "Mouse left down" and "Mouse left up".

States

You can define a pattern that will count as a state change in your application with the states argument. It will print out only lines that match the pattern. It will also print out the last line where the state changed.

$ logal example.log states -P "[\d]{4}-[\d]{2}-[\d]{2} [\d]{2}:[\d]{2}:[\d]{2} " -c 28 "INFO Set state to"

On itself it's basically just a grep but you can combine these features by using a config file.

Using a config file

You can use a config file to combine these log processors. An example config file that combines all the previous commands would look like this:

{
    "prefix": "[\\d]{4}-[\\d]{2}-[\\d]{2} [\\d]{2}:[\\d]{2}:[\\d]{2} ",
    "pattern_colors": [
        { "pattern": "INFO", "color": "28" },
        { "pattern": "WARN", "color": "24" },
        { "pattern": "ERROR", "color": "88" }
    ],
    "event_patterns": [
        {
            "start_pattern": "INFO Mouse left down",
            "end_pattern": "INFO Mouse left up",
            "color": "29"
        }
    ],
    "state_patterns": [
        { "pattern": "INFO Set state to", "color": "30" }
    ]
}

and you can use this config file with the following command line parameters:

$ logan example.log use-config example.json

With a config file you can define multiple event and state as well.

Installation

Currently you have to compile Logan to run it. The plan is to support all three major platform (Windows, Linux, MacOS) with pre-built binaries. You can also use cargo run -- ARGS to run Logan.