Filter results and tabulate output - Alibaba Cloud CLI - Alibaba Cloud Documentation Center

This topic describe how to filter results by using Alibaba Cloud CLI. The filter function of Alibaba Cloud CLI obtains the information that you want in a tabular output. Specifically, this function allows you to quickly obtain the information you want from the JSON structure data that is returned from the query interface of Alibaba Cloud.

--output overview

To make a more intuitive command output result, Alibaba Cloud CLI provides --output option to extract the fields that you want from the results, and the default tabular output. The --output option contains the following fields:


field Name	Description	Additional instructions
cols	The column name of the table. It must correspond to fields in json data.	For example, the ECS DescribeInstances interface returns the fields InstanceId and Status.
rows	Specifies the JMESPath path where the filter field is located.	The jmespath query statement specifies the data source of the table row in the json result.
num	Specifies `num=true` to enable the row number column, starting with the number 0.	The default is `num=false`.

Scenario

Often it can be difficult to find the information you want in the JSON structured data that is returned by the query interface of Alibaba Cloud. As an example, consider the following scenario. Assume that you run the following command to query information about all ECS instances.

aliyun ecs DescribeInstances

The system returns an output similar to the following script:

{
  "PageNumber": 1,
  "TotalCount": 2,
  "Pagesize": 10,
  "RequestId": "2B76ECBD-A296-407E-BE17-7E668A609DDA",
  "Instances": {
    "Instance": [
      {
        "ImageId": "ubuntu_16_0402_64_20G_alibase_20171227.vhd",
        "InstanceTypeFamily": "ecs.xn4",
        "VlanId": "",
        "InstanceId": "i-12345678912345678123",
        "Status": "Stopped",
        //omit some fields
      },
      Instance": [
      {
        "ImageId": "ubuntu1404_64_20G_aliaegis_20150325.vhd",
        "InstanceTypeFamilyId":"ecs.s3",
        "VlanId": "",
        "InstanceId": "I-abcdefghijklmnopqrst ",
        "Status": "Running",
        //omit some fields
      },
    ]
  }
}

From the preceding example, you can see that it can be difficult to extract information from the returned output.

Solution

Run the following command to filter the field RequestId returned in the preceding scenario.

Note Because this field is the root element, you do not need to specify the rows field.
```
aliyun ecs DescribeInstances --output cols=RequestId
```
The system displays output similar to the following:
```
RequestId
---------
2B76ECBD-A296-407E-BE17-7E668A609DDA
```
Run the following command to filter the fields InstanceId and Status returned in the preceding scenario. The JMESPath path of the two fields is Instances.Instance[]. For details about how to write JMESPath, see JMESPath Tutorial.
```
aliyun ecs DescribeInstances --output cols=InstanceId,Status rows=Instances.Instance[]
```
The system displays output similar to the following:
```
InstanceId             | Status
----------             | ------
i-12345678912345678123 | Stopped
i-abcdefghijklmnopqrst | Running
```
If you want to output the row number, specify num=true. The output result is similar to the following:
```
Num | InstanceId             | Status
--- | ----------             | ------
0   | i-12345678912345678123 | Stopped
1   | i-abcdefghijklmnopqrst | Running
```