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https://github.com/brocode/fblog

Small command-line JSON Log viewer
https://github.com/brocode/fblog

command-line command-line-tool json log viewer

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Small command-line JSON Log viewer

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README 

        
![](./logo/fblog_small.png)



# fblog



A small tool to view json log files.



![](demo.png)



## Print specific fields



``` shell-script

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.



```bash

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:



``` shell-script

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



## NO_COLOR



`fblog` disables color output if the `NO_COLOR` environment variable is

present.



[no-color](https://no-color.org/)



## 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

`key`, where it would match a placeholder with the key

`key`.



### Example



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



``` json

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

```



Running with the following arguments:



``` bash

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

```



Result:



![](./res/placeholder-example1.svg)



## Installation



``` bash

cargo install fblog

```



Available in package managers:

[AUR](https://aur.archlinux.org/packages/fblog/),

[brew](https://formulae.brew.sh/formula/fblog)



## Log tailing



`fblog` does not support native log tailing but this is easily

achiveable.



``` bash

tail -f file | fblog

```



Or with kubernetes tooling for example



``` bash

kubectl logs -f ... | fblog

```



In general you can pipe any endless stream to fblog.



## shell completions



```bash

fblog --generate-completions 

```



## 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](./default_config.toml) 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):

```toml

[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/plugin.yml` add this:



```yaml

plugin:

  fblog-pod:

    shortCut: Shift-L

    confirm: false

    description: "fblog"

    scopes:

      - pods

    command: sh

    background: false

    args:

      - -c

      - "kubectl logs --follow -n $NAMESPACE $NAME | 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 | fblog"

  fblog-pod-all:

    shortCut: Shift-A

    confirm: false

    description: "fblog -d"

    scopes:

      - pods

    command: sh

    background: false

    args:

      - -c

      - "kubectl logs --follow -n $NAMESPACE $NAME | fblog -d"

  fblog-container-all:

    shortCut: Shift-A

    confirm: false

    description: "fblog -d"

    scopes:

      - containers

    command: sh

    background: false

    args:

      - -c

      - "kubectl logs  --follow -n $NAMESPACE $POD -c $NAME | fblog -d"

```