json2line

json2line is a tool that takes JSON strings in lines and formats its values to a string. The format can be configured with Go templates.

This can be done as follows:

echo { "key": "value" } | json2-line -f templates.toml -f "my_template"

with a config file

[templates]
my_template = "the value is:'{{ .key }}'"

will output

the value is:'value'

Special characters

If you need to replace keys containing special characters, like e.g. @ a replacement can be defined as follows:

[templates]
my_template = "the value is:'{{ .at_key }}'"
[replacements]
"@"="at_"

Now all occurrences of @ will be replaced with at_. Now, if @key appears in the JSON, it will be renamed to at_key internally so that it can be accessed via {{ .at_key }} as shown in the templates-section.

Configuration

The configuration can be adapted via the command line interface

This can be achieved by the subcommand json2line configure which has two subcommands formatter and replacement which can be used to change the available formatters and replacements, respectively.

Changing the formatter configuration

# add a new formatter with the name 'new_formatter'
json2line configure formatter -k "new_formatter" -v "{{ .someTemplate }}"

# delete a formatter with the name 'new_formatter'
json2line configure formatter -d "new_formatter"                          

Be careful, as this is immediately persisted.

It is also possible to print the current configuration:

json2line configure -s

Buffer Size

Sometimes a line may be too large and the error message

could not parse line: bufio.Scanner: token too long

appears. For such cases it is possible to set the buffer size to a larger value in the configuration via:

json2line configure buffer_size -S <BUFFER_SIZE>

In case this should not be persisted it is possible to just call

json2line -b <BUFFER_SIZE>

in this case nothing gets persisted and the value in the configuration file gets ignored in favor of this value.