Installing the command-line executable

Assuming you have Rust/Cargo installed, run this command in a terminal:

cargo install fblog

It will make the fblog command available in your PATH if you've allowed the PATH to be modified when installing Rust. cargo uninstall fblog uninstalls.

Back to the crate overview.

Readme

fblog

A small tool to view json log files.

Print specific fields

fblog -a message -a "status > a" sample_nested.json.log

Prefix Logs

If your query docker or kubectl for multiple pods it will prefix the log lines: PODNAME | {"message": "test"}. fblog can parse this and add it to the message. Just use -p.

Filter

To filter log messages it is possible to use lua. If you are unsure which variables are available you can use --print-lua to see the code generated by fblog.

fblog -f 'level ~= "info"' # will print all message where the level is not info
fblog -f 'process == "play"' # will print all message where the process is play
fblog -f 'string.find(fu, "bow.*") ~= nil' # will print all messages where fu starts with bow
fblog -f 'process == "play"' # will print all message where the process is play
fblog -f 'process == "rust" and fu == "bower"'
fblog --no-implicit-filter-return-statement -f 'if 3 > 2 then return true else return false end'

# not valid lua identifiers like log.level gets converted to log_level.
# Every character that is not _ or a letter will be converted to _
fblog -d -f 'log_level == "WARN"' sample_elastic.log

# nested fields are converted to lua records
fblog  -d -f 'status.a == 100' sample_nested.json.log

# array fields are converted to lua tables (index starts with 1)
fblog  -d -f 'status.d[2] == "a"' sample_nested.json.log

Customize

fblog tries to detect the message, severity and timestamp of a log entry. This behavior can be customized. See --help for more information.

You can customize fblog messages: Format output:

fblog -p --main-line-format "{{#if short_message}}{{ red short_message }}{{/if}}" sample.json.log

The following sanitized variables are provided by fblog:

fblog_timestamp
fblog_level
fblog_message
fblog_prefix

For the default formatting see --help

Nested values are registered as objects. So you can use nested.value to access nested values.

handlebar helpers:

bold
yellow
red
blue
purple
cyan
green
color_rgb 0 0 0
uppercase
level_style
fixed_size 10
min_size 10

NO_COLOR

fblog disables color output if the NO_COLOR environment variable is present.

no-color

Message placeholder substitution

Placeholders in the message (fblog_message) can be substituted with their corresponding values in a context object or array. To enable substitutions, pass the -s flag or either set context key (-c context) or placeholder format (-F {key}).

Note that the placeholder format should be written like <PREFIX>key<SUFFIX>, where it would match a placeholder with the key key.

Example

Given the following log (referred to as example.log):

{"message": "Found #{count} new items.", "extra_data": {"count": 556}, "level": "info"}

Running with the following arguments:

fblog -c extra_data -F '#{key}' example.log

Result:

Installation

cargo install fblog

Available in package managers: AUR, brew

Log tailing

fblog does not support native log tailing but this is easily achievable.

tail -f file | fblog

Or with kubernetes tooling for example

kubectl logs -f ... | fblog

In general you can pipe any endless stream to fblog.

shell completions

fblog --generate-completions <shell>

configuration file

fblog reads its configuration from a file called fblog.toml, which is located

Linux: $XDG_CONFIG_HOME or $HOME/.config

Windows: {FOLDERID_RoamingAppData}

macOS: $HOME/Library/Application Support

If the file does not exist or is empty this is the default config.

log levels

These levels are colorized by fblog:

trace
debug
info
warn
error
fatal

You can map additional level values (used for output and color):

[level_map]
10 = "trace"
20 = "debug"
30 = "info"
40 = "warn"
50 = "error"
60 = "fatal"
# these values for example are used by https://www.npmjs.com/package/bunyan#levels

k9s

In the file ~/.config/k9s/plugins.yaml add this:

plugins:
  fblog-pod:
    shortCut: Shift-L
    confirm: false
    description: "fblog"
    scopes:
      - pods
    command: sh
    background: false
    args:
      - -c
      - "kubectl logs --follow -n $NAMESPACE $NAME --context $CONTEXT | fblog"
  fblog-container:
    shortCut: Shift-L
    confirm: false
    description: "fblog"
    scopes:
      - containers
    command: sh
    background: false
    args:
      - -c
      - "kubectl logs  --follow -n $NAMESPACE $POD -c $NAME --context $CONTEXT | fblog"
  fblog-pod-all:
    shortCut: Shift-K
    confirm: false
    description: "fblog -d"
    scopes:
      - pods
    command: sh
    background: false
    args:
      - -c
      - "kubectl logs --follow -n $NAMESPACE $NAME --context $CONTEXT | fblog -d"
  fblog-container-all:
    shortCut: Shift-K
    confirm: false
    description: "fblog -d"
    scopes:
      - containers
    command: sh
    background: false
    args:
      - -c
      - "kubectl logs  --follow -n $NAMESPACE $POD -c $NAME --context $CONTEXT | fblog -d"