# Standard Input The **stdin** plugin supports retrieving a message stream from the standard input interface (stdin) of the Fluent Bit process. In order to use it, specify the plugin name as the input, e.g: ```bash $ fluent-bit -i stdin -o stdout ``` If the stdin stream is closed (end-of-file), the stdin plugin will instruct Fluent Bit to exit with success (0) after flushing any pending output. ## Input formats If no parser is configured for the stdin plugin, it expects *valid JSON* input data in one of the following formats: 1. A JSON object with one or more key-value pairs: `{ "key": "value", "key2": "value2" }` 2. A 2-element JSON array in [Fluent Bit Event](/manual/2.1/concepts/key-concepts.md#event-or-record) format, which may be: * `[TIMESTAMP, { "key": "value" }]` where TIMESTAMP is a floating point value representing a timestamp in seconds; or * from Fluent Bit v2.1.0, `[[TIMESTAMP, METADATA], { "key": "value" }]` where TIMESTAMP has the same meaning as above and and METADATA is a JSON object. Multi-line input JSON is supported. Any input data that is *not* in one of the above 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-example) for sample configuration. ## Log event timestamps The Fluent Bit event timestamp will be set from the input record if the 2-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 example A better example to demonstrate how it works will be through a *Bash* script that generates messages and writes them to [Fluent Bit](http://fluentbit.io). Write the following content in a file named *test.sh*: ```bash #!/bin/sh for ((i=0; i<=5; i++)); do echo -n "{\"key\": \"some value\"}" sleep 1 done ``` Now lets start the script and [Fluent Bit](http://fluentbit.io): ```bash $ bash test.sh | fluent-bit -q -i stdin -o stdout [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 example An input event timestamp may also be supplied. Replace `test.sh` with: ```bash #!/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 ``` Re-run the sample command. Note that the timestamps output by Fluent Bit are now one day old because Fluent Bit used the input message timestamp. ```bash $ bash test.sh | fluent-bit -q -i stdin -o stdout [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 example Additional metadata is also supported on Fluent Bit v2.1.0 and above by replacing the timestamp with a 2-element object, e.g.: ```bash #!/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 ``` ``` $ bash ./test.sh | fluent-bit -q -i stdin -o stdout [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}] ``` On older Fluent Bit versions records in this format will be discarded. Fluent Bit will log: ``` [ warn] unknown time format 6 ``` if the log level permits. ### Parser input example 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 `parser.conf` that captures the whole message line: ``` [PARSER] name stringify_message format regex Key_Name message regex ^(?.*) ``` then use that in the `parser` clause of the stdin plugin in the `fluent-bit.conf`: ``` [INPUT] Name stdin Tag stdin Parser stringify_message [OUTPUT] Name stdout Match * ``` Fluent Bit will now read each line and emit a single message for each input line: ``` $ seq 1 5 | /opt/fluent-bit/bin/fluent-bit -c fluent-bit.conf -R parser.conf -q [0] stdin: [1681358780.517029169, {"message"=>"1"}] [1] stdin: [1681358780.517068334, {"message"=>"2"}] [2] stdin: [1681358780.517072116, {"message"=>"3"}] [3] stdin: [1681358780.517074758, {"message"=>"4"}] [4] stdin: [1681358780.517077392, {"message"=>"5"}] $ ``` In real-world deployments it is best to use a more realistic parser that splits messages into real fields and adds appropriate tags. ## 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. The value must be according to the [Unit Size](/manual/2.1/administration/configuring-fluent-bit/unit-sizes.md) specification. | 16k | | Parser | The name of the parser to invoke instead of the default JSON input parser | | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.fluentbit.io/manual/2.1/pipeline/inputs/standard-input.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. 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