# Standard input {% hint style="info" %} **Supported event types:** `logs` {% endhint %} The *Standard input* plugin supports retrieving a message stream from the standard input interface (`stdin`) of the Fluent Bit process. To use it, specify the plugin name as the input. For example: ```shell fluent-bit -i stdin -o stdout ``` If the `stdin` stream is closed (`end-of-file`), the plugin instructs Fluent Bit to exit with success (`0`) after flushing any pending output. ## Configuration parameters The plugin supports the following configuration parameters: | Key | Description | Default | | ------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- | | `buffer_size` | Set the buffer size to read data. This value is used to increase buffer size and must be set according to the [Unit Size](https://docs.fluentbit.io/manual/administration/configuring-fluent-bit#unit-sizes) specification. | `16k` | | `parser` | The name of the parser to invoke instead of the default JSON input parser. | *none* | | `threaded` | Indicates whether to run this input in its own [thread](https://docs.fluentbit.io/manual/administration/multithreading#inputs). | `false` | ## Input formats If no parser is configured for the `stdin` plugin, it expects valid JSON input data in one of the following formats: * A JSON object with one or more key-value pairs: `{ "key": "value", "key2": "value2" }` * A 2-element JSON array in [Fluent Bit Event](https://docs.fluentbit.io/manual/concepts/key-concepts#event-or-record) format, which can be: * `[TIMESTAMP, { "key": "value" }]` where TIMESTAMP is a floating point value representing a timestamp in seconds. * From Fluent Bit v2.1.0, `[[TIMESTAMP, METADATA], { "key": "value" }]` where *`TIMESTAMP`* has the same meaning as previous and *`METADATA`* is a JSON object. Multi-line input JSON is supported. Any input data which isn't in one of the supported formats will cause the plugin to log errors like: ``` [debug] [input:stdin:stdin.0] invalid JSON message, skipping [error] [input:stdin:stdin.0] invalid record found, it's not a JSON map or array ``` To handle inputs in other formats, a parser must be explicitly specified in the configuration for the `stdin` plugin. See [parser input example](#parser-input) for sample configuration. ## Log event timestamps The Fluent Bit event timestamp will be set from the input record if the two-element event input is used or a custom parser configuration supplies a timestamp. Otherwise, the event timestamp will be set to the timestamp at which the record is read by the `stdin` plugin. ## Examples ### JSON input To demonstrate how the plugin works, you can use a `bash` script that generates messages and writes them to [Fluent Bit](https://fluentbit.io). 1. Write the following content in a file named `test.sh`: ```shell #!/bin/sh for ((i=0; i<=5; i++)); do echo -n "{\"key\": \"some value\"}" sleep 1 done ``` 2. Start the script and [Fluent Bit](https://fluentbit.io): ```shell bash test.sh | fluent-bit -q -i stdin -o stdout ``` 3. The command should return output like the following: ``` [0] stdin.0: [[1684196745.942883835, {}], {"key"=>"some value"}] [0] stdin.0: [[1684196746.938949056, {}], {"key"=>"some value"}] [0] stdin.0: [[1684196747.940162493, {}], {"key"=>"some value"}] [0] stdin.0: [[1684196748.941392297, {}], {"key"=>"some value"}] [0] stdin.0: [[1684196749.942644238, {}], {"key"=>"some value"}] [0] stdin.0: [[1684196750.943721442, {}], {"key"=>"some value"}] ``` ### JSON input with timestamp 1. An input event timestamp can also be supplied. Replace `test.sh` with: ```shell #!/bin/sh for ((i=0; i<=5; i++)); do echo -n " [ $(date '+%s.%N' -d '1 day ago'), { \"realtimestamp\": $(date '+%s.%N') } ] " sleep 1 done ``` 2. Re-run the sample command. Timestamps output by Fluent Bit are now one day old because Fluent Bit used the input message timestamp. ```shell bash test.sh | fluent-bit -q -i stdin -o stdout ``` 3. Which returns the following: ``` [0] stdin.0: [[1684110480.028171300, {}], {"realtimestamp"=>1684196880.030070}] [0] stdin.0: [[1684110481.033753395, {}], {"realtimestamp"=>1684196881.034741}] [0] stdin.0: [[1684110482.036730051, {}], {"realtimestamp"=>1684196882.037704}] [0] stdin.0: [[1684110483.039903879, {}], {"realtimestamp"=>1684196883.041081}] [0] stdin.0: [[1684110484.044719457, {}], {"realtimestamp"=>1684196884.046404}] [0] stdin.0: [[1684110485.048710107, {}], {"realtimestamp"=>1684196885.049651}] ``` ### JSON input with metadata 1. Additional metadata is supported in Fluent Bit v2.1.0 and later by replacing the timestamp with a two-element object. For example: ```shell #!/bin/sh for ((i=0; i<=5; i++)); do echo -n " [ [ $(date '+%s.%N' -d '1 day ago'), {\"metakey\": \"metavalue\"} ], { \"realtimestamp\": $(date '+%s.%N') } ] " sleep 1 done ``` 2. Run test using the command: ```shell bash ./test.sh | fluent-bit -q -i stdin -o stdout ``` 3. Which returns results like the following: ``` [0] stdin.0: [[1684110513.060139417, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196913.061017}] [0] stdin.0: [[1684110514.063085317, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196914.064145}] [0] stdin.0: [[1684110515.066210508, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196915.067155}] [0] stdin.0: [[1684110516.069149971, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196916.070132}] [0] stdin.0: [[1684110517.072484016, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196917.073636}] [0] stdin.0: [[1684110518.075428724, {"metakey"=>"metavalue"}], {"realtimestamp"=>1684196918.076292}] ``` 4. On older Fluent Bit versions records in this format will be discarded. If the log level permits, Fluent Bit will log: ``` [ warn] unknown time format 6 ``` ### Parser input To capture inputs in other formats, specify a parser configuration for the `stdin` plugin. For example, if you want to read raw messages line by line and forward them, you could use a separate parsers file that captures the whole message line: {% tabs %} {% tab title="parsers.yaml" %} ```yaml parsers: - name: stringify_message format: regex key_name: message regex: '^(?.*)' ``` {% endtab %} {% tab title="parsers.conf" %} ``` [PARSER] Name stringify_message Format regex Key_Name message Regex ^(?.*) ``` {% endtab %} {% endtabs %} You can then use the parsers file in a `stdin` plugin in the main Fluent Bit configuration file as follows: {% tabs %} {% tab title="fluent-bit.yaml" %} ```yaml service: parsers_file: parsers.yaml pipeline: inputs: - name: stdin tag: stdin parser: stringify_message outputs: - name: stdout match: '*' ``` {% endtab %} {% tab title="fluent-bit.conf" %} ``` [SERVICE] Parsers_File parsers.conf [INPUT] Name stdin Tag stdin Parser stringify_message [OUTPUT] Name stdout Match * ``` {% endtab %} {% endtabs %} Fluent Bit will now read each line and emit a single message for each input line, using the following command: ```shell # For YAML configuration. seq 1 5 | ./fluent-bit --config fluent-bit.yaml # For classic configuration. seq 1 5 | ./fluent-bit --config fluent-bit.conf ``` Which returns output similar to: ``` ... [0] stdin: [[1751545974.960182000, {}], {"message"=>"1"}] [1] stdin: [[1751545974.960246000, {}], {"message"=>"2"}] [2] stdin: [[1751545974.960255000, {}], {"message"=>"3"}] [3] stdin: [[1751545974.960262000, {}], {"message"=>"4"}] [4] stdin: [[1751545974.960268000, {}], {"message"=>"5"}] ... ``` In production deployments it's best to use a parser that splits messages into real fields and adds appropriate tags.