Control instructions - Simple Log Service - Alibaba Cloud Documentation Center

This topic describes how to use control instructions and provides examples.

.let

Defines a named dataset to use as input for subsequent Structured Process Language (SPL) expressions. For more information about SPL datasets, see SPL datasets.

Syntax

.let <dataset>=<spl-expr>

Parameters

Parameter	Type	Required	Description
dataset	String	Yes	The name of the dataset. The name can contain letters, digits, and underscores (_). It must start with a letter and is case-sensitive.
spl-expr	SPLExp	Yes	The SPL expression that generates the dataset.

Example

Filter and classify access logs by status code and output the results.

SPL statement

-- Define the SPL processing result as the named dataset 'src' to use as input for subsequent SPL expressions.
.let src = * 
| where status=cast(status as BIGINT);

-- Use the named dataset 'src' as input. Filter for data where the status field is 5xx. Define the result as the dataset 'err'. Do not output the result.
.let err = $src
| where status >= 500
| extend msg='ERR';

-- Use the named dataset 'src' as input. Filter for data where the status field is 2xx. Define the result as the dataset 'ok'. Do not output the result.
.let ok = $src
| where status >= 200 and status < 300
| extend msg='OK';

-- Output the named datasets 'err' and 'ok'.
$err;
$ok;

Input data

# Entry 1
status: '200'
body: 'this is a test'

# Entry 2
status: '500'
body: 'internal error'

# Entry 3
status: '404'
body: 'not found'

Output

# Entry 1: Dataset is 'err'
status: '500'
body: 'internal error'
msg: 'ERR'

# Entry 2: Dataset is 'ok'
status: '200'
body: 'this is a test'
msg: 'OK'