In this lesson, we will cover:

  • What is TextFSM?
  • How to use TextFSM parsers in Netmiko.
  • How to build a custom TextFSM parsing template.

The scripts and code for this lesson can be found within the Netmiko repo under the directory: examples/parsing/textfsm.

TextFSM Overview

TextFSM is a Python module developed by Google that allows you to take unstructured data and convert it to structured data via sets of regex-based templates. An example of a TextFSM template for parsing the output of show_version on an EOS is shown below:

Value MODEL (\S+)
Value HW_VERSION (\S+)
Value SERIAL_NUMBER (\S+)
Value SYS_MAC (\S+)
Value IMAGE (\S+)
Value TOTAL_MEMORY (\d+)
Value FREE_MEMORY (\d+)

Start
  ^Arista\s+${MODEL}
  ^Hardware\s+version:\s+${HW_VERSION}
  ^Serial\s+number:\s+${SERIAL_NUMBER}
  ^System\s+MAC\s+address:\s+${SYS_MAC}
  ^Software\s+image\s+version:\s+${IMAGE}
  ^Total\s+memory:\s+${TOTAL_MEMORY}
  ^Free\s+memory:\s+${FREE_MEMORY} -> Record
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