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Updated head input plugin doc for standards and order. Fixes #2260. (#2261)
Updated head input plugin doc for standards and order. Fixes #2260. Signed-off-by: Eric D. Schabell <eric@schabell.org>
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‎pipeline/inputs/head.md‎

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@@ -6,19 +6,95 @@ The _Head_ input plugin reads events from the head of a file. Its behavior is si
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The plugin supports the following configuration parameters:
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| Key | Description |
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|:----------------|:--------------------------------------------------------------------------------------------------------------------------|
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| `File` | Absolute path to the target file. For example: `/proc/uptime`. |
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| `Buf_Size` | Buffer size to read the file. |
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| `Interval_Sec` | Polling interval (seconds). |
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| `Interval_NSec` | Polling interval (nanoseconds). |
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| `Add_Path` | If enabled, the path is appended to each records. Default: `false`. |
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| `Key` | Rename a key. Default: `head`. |
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| `Lines` | Line number to read. If the number N is set, `in_head` reads first N lines like `head(1) -n`. |
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| `Split_line` | If enabled, `in_head` generates key-value pair per line. |
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| `Threaded` | Indicates whether to run this input in its own [thread](../../administration/multithreading.md#inputs). Default: `false`. |
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### Split line mode
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| Key | Description | Default |
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|:----------------|:--------------------------------------------------------------------------------------------------------|:--------|
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| `Add_Path` | If enabled, the path is appended to each record. | `false` |
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| `Buf_Size` | Buffer size to read the file. | `256` |
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| `File` | Absolute path to the target file. For example: `/proc/uptime`. | _none_ |
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| `Interval_NSec` | Polling interval (nanoseconds). | `0` |
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| `Interval_Sec` | Polling interval (seconds). | `1` |
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| `Key` | Rename a key. | `head` |
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| `Lines` | Line number to read. If the number N is set, `in_head` reads first N lines like `head(1) -n`. | `0` |
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| `Split_line` | If enabled, `in_head` generates key-value pair per line. | `false` |
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| `Threaded` | Indicates whether to run this input in its own [thread](../../administration/multithreading.md#inputs). | `false` |
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## Getting started
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To read the head of a file, you can run the plugin from the command line or through the configuration file.
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### Command line
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The following example will read events from the `/proc/uptime` file, tag the records with the `uptime` name and flush them back to the `stdout` plugin:
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```shell
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fluent-bit -i head -t uptime -p File=/proc/uptime -o stdout -m '*'
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```
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The output will look similar to:
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```text
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Fluent Bit v1.x.x
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* Copyright (C) 2019-2020 The Fluent Bit Authors
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* Copyright (C) 2015-2018 Treasure Data
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* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
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* https://fluentbit.io
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[2016/05/17 21:53:54] [ info] starting engine
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[0] uptime: [1463543634, {"head"=>"133517.70 194870.97"}]
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[1] uptime: [1463543635, {"head"=>"133518.70 194872.85"}]
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[2] uptime: [1463543636, {"head"=>"133519.70 194876.63"}]
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[3] uptime: [1463543637, {"head"=>"133520.70 194879.72"}]
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```
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### Configuration file
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In your main configuration file append the following:
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{% tabs %}
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{% tab title="fluent-bit.yaml" %}
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```yaml
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pipeline:
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inputs:
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- name: head
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tag: uptime
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file: /proc/uptime
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buf_size: 256
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interval_sec: 1
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interval_nsec: 0
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outputs:
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- name: stdout
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match: '*'
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```
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{% endtab %}
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{% tab title="fluent-bit.conf" %}
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```text
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[INPUT]
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Name head
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Tag uptime
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File /proc/uptime
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Buf_Size 256
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Interval_Sec 1
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Interval_NSec 0
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[OUTPUT]
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Name stdout
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Match *
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```
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{% endtab %}
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{% endtabs %}
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The interval is calculated like this:
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`Total interval (sec) = Interval_Sec + (Interval_Nsec / 1000000000)`.
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For example: `1.5s = 1s + 500000000ns`.
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## Split line mode
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Use this mode to get a specific line. The following example gets CPU frequency from `/proc/cpuinfo`.
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```yaml
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pipeline:
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inputs:
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- name: head
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tag: head.cpu
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file: /proc/cpuinfo
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lines: 8
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split_line: true
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filters:
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- name: record_modifier
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match: '*'
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whitelist_key: line7
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outputs:
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- name: stdout
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match: '*'
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inputs:
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- name: head
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tag: head.cpu
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file: /proc/cpuinfo
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lines: 8
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split_line: true
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filters:
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- name: record_modifier
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match: '*'
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whitelist_key: line7
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outputs:
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- name: stdout
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match: '*'
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```
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{% endtab %}
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{% tab title="fluent-bit.conf" %}
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```text
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[INPUT]
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Name head
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Tag head.cpu
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File /proc/cpuinfo
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Lines 8
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Split_line true
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# {"line0":"processor : 0", "line1":"vendor_id : GenuineIntel" ...}
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Name head
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Tag head.cpu
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File /proc/cpuinfo
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Lines 8
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Split_line true
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# {"line0":"processor : 0", "line1":"vendor_id : GenuineIntel" ...}
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[FILTER]
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Name record_modifier
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Match *
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Whitelist_key line7
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Name record_modifier
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Match *
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Whitelist_key line7
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[OUTPUT]
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Name stdout
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Match *
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Name stdout
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Match *
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```
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{% endtab %}
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[2] head.cpu: [1498484307.010042482, {"line7"=>"cpu MHz : 2791.009"}]
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[3] head.cpu: [1498484308.008447978, {"line7"=>"cpu MHz : 2791.009"}]
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```
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## Get started
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To read the head of a file, you can run the plugin from the command line or through the configuration file.
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### Command line
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The following example will read events from the `/proc/uptime` file, tag the records with the `uptime` name and flush them back to the `stdout` plugin:
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```shell
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fluent-bit -i head -t uptime -p File=/proc/uptime -o stdout -m '*'
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```
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The output will look similar to:
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```text
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Fluent Bit v1.x.x
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* Copyright (C) 2019-2020 The Fluent Bit Authors
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* Copyright (C) 2015-2018 Treasure Data
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* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
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* https://fluentbit.io
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[2016/05/17 21:53:54] [ info] starting engine
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[0] uptime: [1463543634, {"head"=>"133517.70 194870.97"}]
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[1] uptime: [1463543635, {"head"=>"133518.70 194872.85"}]
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[2] uptime: [1463543636, {"head"=>"133519.70 194876.63"}]
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[3] uptime: [1463543637, {"head"=>"133520.70 194879.72"}]
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```
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### Configuration file
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In your main configuration file append the following:
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{% tabs %}
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{% tab title="fluent-bit.yaml" %}
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```yaml
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pipeline:
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inputs:
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- name: head
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tag: uptime
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file: /proc/uptime
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buf_size: 256
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interval_sec: 1
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interval_nsec: 0
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outputs:
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- name: stdout
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match: '*'
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```
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{% endtab %}
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{% tab title="fluent-bit.conf" %}
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```shell
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[INPUT]
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Name head
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Tag uptime
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File /proc/uptime
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Buf_Size 256
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Interval_Sec 1
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Interval_NSec 0
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[OUTPUT]
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Name stdout
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Match *
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```
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{% endtab %}
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{% endtabs %}
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The interval is calculated like this:
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`Total interval (sec) = Interval_Sec + (Interval_Nsec / 1000000000)`.
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For example: `1.5s = 1s + 500000000ns`.

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