TxtFSM

An independent TypeScript implementation of TextFSM. TxtFSM turns semi-structured text, such as network device command output, into rows or JavaScript objects using TextFSM templates.

Documentation & Playground

Note

This project is under development and is not affiliated with Google or the original TextFSM project. It is based on the Apache 2.0-licensed original project and is released under the same license.

Features

• Parse TextFSM templates and input entirely in JavaScript or TypeScript
• Return records as arrays or objects keyed by the template header
• Support multiple states and the Required, Filldown, Fillup, List, and Key value options
• Support TextFSM rule actions including Record, NoRecord, Clear, Clearall, Next, Continue, and Error
• Select templates from a TextFSM CLI table index and merge multi-template results by key
• Ship ESM, CommonJS, and TypeScript declarations

Node.js support

Node.js 22.12.0 or later is the supported range. Earlier versions may work, but have not been verified.

Installation

From npm:

npm install txtfsm

From JSR:

npx jsr add @txtfsm/txtfsm

Quick start

See the documentation & playground for a live demo.

API

TxtFSM

Create a reusable parser from a template:

const fsm = new TxtFSM(template);

const rows = fsm.parseText(input);
// TextFSMRow[]; each field is a string or, for Value List, string[]

const records = fsm.parseTextToDicts(input);
// TextFSMRecord[]; Value List properties remain string[]

For example, Value List VLAN produces { VLAN: ['10', '11'] } rather than a comma-delimited string.

Both parsing methods accept { eof: false } as a second argument to disable the implicit EOF record operation.

For one-off parsing, equivalent helper functions are available:

import { parseText, parseTextToDicts } from 'txtfsm';

const rows = parseText(template, input);
const records = parseTextToDicts(template, input);

parseTemplate

parseTemplate(source) validates and compiles a template, returning its value and state definitions. Invalid templates throw TxtFSMTemplateError; runtime parsing failures throw TxtFSMError.

CliTable

CliTable selects a template using an index compatible with TextFSM CLI tables. Provide the index text and a loader that returns template text by file name:

import { CliTable } from 'txtfsm';

const index = `Template, Platform, Command
show_items.textfsm, demo_os, sh[[ow]] it[[ems]]`;

const templates = new Map([
  [
    'show_items.textfsm',
    ['Value ID (\\d+)', 'Value STATE (\\w+)', '', 'Start', '  ^Item ${ID} ${STATE} -> Record'].join(
      '\n',
    ),
  ],
]);

const table = new CliTable(index, (name) => templates.get(name));
const records = table.parseCmd('Item 1 up', {
  Platform: 'demo_os',
  Command: 'show items',
});

// [{ ID: '1', STATE: 'up' }]

Abbreviated command patterns such as sh[[ow]] are supported. An index entry may also list multiple templates separated by :; their records are merged using values marked with the Key option. A missing matching row or template throws CliTableError.

Compatibility

TxtFSM aims to provide behavior compatible with Google TextFSM 2.1.0 for the supported syntax. Compatibility is checked against templates from ntc-templates. Because JavaScript and Python regular expression engines differ, templates that depend on Python-specific regex behavior may not be fully compatible. Please report reproducible differences through GitHub Issues.

Development

See CONTRIBUTING.md for the full contribution workflow.

License

Copyright 2026 yuyosy

The core library includes a TypeScript adaptation of portions of Google TextFSM:

• https://github.com/google/textfsm

Applicable portions:

Copyright 2010, 2011, 2012, 2022 Google Inc. All Rights Reserved. Google TextFSM and this adaptation are licensed under the Apache License, Version 2.0.

For detailed attribution and a record of modifications, see the NOTICE file.