Ansible Pilot

Filter A List By Its Attributes - Ansible selectattr filter

How to list only the enabled features in a network interface using Ansible System Information (Facts) and selectattr filter.

May 9, 2022
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How to Filter A List By Its Attributes in an Ansible Playbook?

I’m going to show you a live demo with some simple Ansible code. I’m Luca Berton and welcome to today’s episode of Ansible Pilot.

selectattr filter in Ansible Playbook?

Today we’re talking about Ansible selectattr Jinja filter. Filters a sequence of objects by applying a test to the specified attribute of each object, and only selecting the objects with the test succeeding. If no test is specified, the attribute’s value will be evaluated as a boolean. The two examples explain how-to for a specific attribute or value using a users list example.

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demo

How to filter a list by its attributes in an Ansible Playbook. I’m going to use the selectattr filter to select only one information from Ansible System Information (Facts). Specifically, I’m going to filter only for enabled features in a network interface (eth1).

code

---
- name: selectattr demo
  hosts: all
  gather_facts: true
  tasks:
    - name: all features
      ansible.builtin.debug:
        var: 'ansible_facts.eth1.features'
    - name: filter enabled
      ansible.builtin.debug:
        msg: "{{ (ansible_facts.eth1.features | dict2items | selectattr('value', 'match', 'on') ) }}"

execution

ansible-pilot $ ansible-playbook -i virtualmachines/demo/inventory variables/selectattr.yml
PLAY [selectattr demo] ****************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [all features] *******************************************************************************
ok: [demo.example.com] => {
    "ansible_facts.eth1.features": {
        "esp_hw_offload": "off [fixed]",
        "esp_tx_csum_hw_offload": "off [fixed]",
        "fcoe_mtu": "off [fixed]",
        "generic_receive_offload": "on",
        "generic_segmentation_offload": "on",
        "highdma": "off [fixed]",
        "hw_tc_offload": "off [fixed]",
        "l2_fwd_offload": "off [fixed]",
        "large_receive_offload": "off [fixed]",
        "loopback": "off [fixed]",
        "netns_local": "off [fixed]",
        "ntuple_filters": "off [fixed]",
        "receive_hashing": "off [fixed]",
        "rx_all": "off",
        "rx_checksumming": "off",
        "rx_fcs": "off",
        "rx_gro_hw": "off [fixed]",
        "rx_gro_list": "off",
        "rx_udp_gro_forwarding": "off",
        "rx_udp_tunnel_port_offload": "off [fixed]",
        "rx_vlan_filter": "on [fixed]",
        "rx_vlan_offload": "on",
        "rx_vlan_stag_filter": "off [fixed]",
        "rx_vlan_stag_hw_parse": "off [fixed]",
        "scatter_gather": "on",
        "tcp_segmentation_offload": "on",
        "tls_hw_record": "off [fixed]",
        "tls_hw_rx_offload": "off [fixed]",
        "tls_hw_tx_offload": "off [fixed]",
        "tx_checksum_fcoe_crc": "off [fixed]",
        "tx_checksum_ip_generic": "on",
        "tx_checksum_ipv4": "off [fixed]",
        "tx_checksum_ipv6": "off [fixed]",
        "tx_checksum_sctp": "off [fixed]",
        "tx_checksumming": "on",
        "tx_esp_segmentation": "off [fixed]",
        "tx_fcoe_segmentation": "off [fixed]",
        "tx_gre_csum_segmentation": "off [fixed]",
        "tx_gre_segmentation": "off [fixed]",
        "tx_gso_list": "off [fixed]",
        "tx_gso_partial": "off [fixed]",
        "tx_gso_robust": "off [fixed]",
        "tx_ipxip4_segmentation": "off [fixed]",
        "tx_ipxip6_segmentation": "off [fixed]",
        "tx_lockless": "off [fixed]",
        "tx_nocache_copy": "off",
        "tx_scatter_gather": "on",
        "tx_scatter_gather_fraglist": "off [fixed]",
        "tx_sctp_segmentation": "off [fixed]",
        "tx_tcp6_segmentation": "off [fixed]",
        "tx_tcp_ecn_segmentation": "off [fixed]",
        "tx_tcp_mangleid_segmentation": "off",
        "tx_tcp_segmentation": "on",
        "tx_tunnel_remcsum_segmentation": "off [fixed]",
        "tx_udp_segmentation": "off [fixed]",
        "tx_udp_tnl_csum_segmentation": "off [fixed]",
        "tx_udp_tnl_segmentation": "off [fixed]",
        "tx_vlan_offload": "on [fixed]",
        "tx_vlan_stag_hw_insert": "off [fixed]",
        "vlan_challenged": "off [fixed]"
    }
}
TASK [filter enabled] *****************************************************************************
ok: [demo.example.com] => {
    "msg": [
        {
            "key": "tx_checksumming",
            "value": "on"
        },
        {
            "key": "tx_checksum_ip_generic",
            "value": "on"
        },
        {
            "key": "scatter_gather",
            "value": "on"
        },
        {
            "key": "tx_scatter_gather",
            "value": "on"
        },
        {
            "key": "tcp_segmentation_offload",
            "value": "on"
        },
        {
            "key": "tx_tcp_segmentation",
            "value": "on"
        },
        {
            "key": "generic_segmentation_offload",
            "value": "on"
        },
        {
            "key": "generic_receive_offload",
            "value": "on"
        },
        {
            "key": "rx_vlan_offload",
            "value": "on"
        },
        {
            "key": "tx_vlan_offload",
            "value": "on [fixed]"
        },
        {
            "key": "rx_vlan_filter",
            "value": "on [fixed]"
        }
    ]
}
PLAY RECAP ****************************************************************************************
demo.example.com           : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
ansible-pilot $

code with ❤️ in GitHub

Recap

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