Urbit
  • Introduction
  • Development

    • Getting Started
    • Environment Setup
    • Grants Program
    • Project Repositories
    • Precepts
    • System Overview

      • Arvo
      • Hoon
      • Nock
      • Vere
      • Azimuth
      • Cryptography
      • Arvo

        • Overview
        • Ames

          • Overview
          • Cryptography
          • API Reference
          • Scry Reference
          • Data Types
          • Behn

            • Overview
            • API Reference
            • Scry Reference
            • Examples
            • Clay

              • Overview
              • Architecture
              • Using Clay
              • Data Types
              • Scry Reference
              • API Reference
              • Examples
              • Marks

                • Overview
                • Writing Marks
                • Using Marks
                • Examples
              • Dill

                • Overview
                • API Reference
                • Scry Reference
                • Data Types
                • Eyre

                  • Overview
                  • External API Reference
                  • Internal API Reference
                  • Scry Reference
                  • Data Types
                  • Guide
                  • Ford

                    • Overview
                    • Gall

                      • Overview
                      • API Reference
                      • Data Types
                      • Iris

                        • Overview
                        • API Reference
                        • Data Types
                        • Example
                        • Jael

                          • Overview
                          • API Reference
                          • Scry Reference
                          • Data Types
                          • Examples
                          • Concepts

                            • Scries
                            • Subscriptions
                            • Tutorials

                              • Move Trace
                              • Reference

                                • Cryptography
                                • Filesystem Hierarchy
                              • Userspace

                                • Overview
                                • HTTP API Guide
                                • Gall Guide

                                  • Introduction
                                  • 1. Arvo
                                  • 2. The Agent Core
                                  • 3. Imports and Aliases
                                  • 4. Lifecycle
                                  • 5. Cards
                                  • 6. Pokes
                                  • 7. Structures and Marks
                                  • 8. Subscriptions
                                  • 9. Vanes
                                  • 10. Scries
                                  • 11. Failure
                                  • 12. Next Steps
                                  • Appendix: Types
                                  • Full-Stack Walkthrough

                                    • 1. Introduction
                                    • 2. Types
                                    • 3. Agent
                                    • 4. JSON
                                    • 5. Marks
                                    • 6. Eyre
                                    • 7. React app setup
                                    • 8. React app logic
                                    • 9. Desk and glob
                                    • 10. Summary
                                    • Graph Store

                                      • Graph Store Overview
                                      • Data Structure Overview
                                      • Validator Walkthrough
                                      • Sample Application: Library
                                      • Graph Store - Reference
                                      • Advanced Info
                                      • Threads

                                        • Overview
                                        • HTTP API
                                        • Reference
                                        • Basics

                                          • Fundamentals
                                          • Bind
                                          • Input
                                          • Output
                                          • Summary
                                          • Gall

                                            • Start Thread
                                            • Take Result
                                            • Take Facts
                                            • Stop Thread
                                            • Poke Thread
                                            • Examples

                                              • Fetch JSON
                                              • Child Thread
                                              • Main-loop
                                              • Poke Agent
                                              • Scry
                                              • Take Fact
                                            • Distribution

                                              • Overview
                                              • Guide
                                              • Docket File
                                              • Glob
                                              • Dojo Tools
                                            • Hoon

                                              • Overview
                                              • Hoon School

                                                • 1.1 Introduction
                                                • 1.1.1 Walkthrough: List of Numbers
                                                • 1.2 Nouns
                                                • 1.3 Hoon Syntax
                                                • 1.3.1 Walkthrough: Conditionals
                                                • 1.4 Gates (Hoon Functions)
                                                • 1.4.1 Walkthrough: Recursion
                                                • 1.5 Lists
                                                • 1.5.1 Walkthrough: Fibonacci Sequence
                                                • 1.6 The Subject and Its Legs
                                                • 1.6.1 Walkthrough: Ackermann Function
                                                • 1.7 Arms and Cores
                                                • 1.7.1 Walkthrough: Caesar Cipher
                                                • 1.8 Doors
                                                • 1.8.1 Bank Account
                                                • 1.9 Generators
                                                • 2.1 Atoms, Auras, and Simple Cell Types
                                                • 2.2 Type Checking and Type Inference
                                                • 2.3 Structures and Complex Types
                                                • 2.3.1 Walkthrough: Libraries
                                                • 2.3.2 Molds
                                                • 2.4 Standard Library: Trees, Sets, and Maps
                                                • 2.5 Type Polymorphism
                                                • 2.5.1 Walkthrough: Iron Polymorphism and Wet Polymorphism
                                                • 2.5.2 Walkthrough: Lead Polymorphism
                                                • 2.6 Behn
                                                • 2.7 Gall
                                                • 2.7.1 Gall Walkthrough: Egg Timer
                                                • Guides

                                                  • CLI apps
                                                  • Parsing
                                                  • JSON
                                                  • Strings
                                                  • Sail (HTML)
                                                  • Writing Aqua Tests
                                                  • Reference

                                                    • Cheat Sheet
                                                    • Irregular forms
                                                    • Hoon Errors
                                                    • Hoon Style Guide
                                                    • Basic Types
                                                    • Advanced Types
                                                    • Auras
                                                    • Runes

                                                      • Atoms and strings
                                                      • Nock . ('dot')
                                                      • Wild ! ('zap')
                                                      • Change Subject = ('tis')
                                                      • Conditionals ? ('wut')
                                                      • Cores | ('bar')
                                                      • Arms + ('lus')
                                                      • Cells : ('col')
                                                      • Calls % ('cen')
                                                      • Casts ^ ('ket')
                                                      • Structures $ ('buc')
                                                      • Make ; ('mic')
                                                      • Hints ~ ('sig')
                                                      • Imports / ('fas')
                                                      • Terminators -- and ==
                                                      • Limbs and wings

                                                        • Limbs
                                                        • Wings
                                                        • Standard library

                                                          • Table of Contents
                                                          • 1a: Basic Arithmetic
                                                          • 1b: Tree Addressing
                                                          • 1c: Molds and Mold-Builders
                                                          • 2a: Unit Logic
                                                          • 2b: List Logic
                                                          • 2c: Bit Arithmetic
                                                          • 2d: Bit Logic
                                                          • 2e: Insecure Hashing
                                                          • 2f: Noun Ordering
                                                          • 2g: Unsigned Powers
                                                          • 2h: Set Logic
                                                          • 2i: Map Logic
                                                          • 2j: Jar and Jug Logic
                                                          • 2k: Queue Logic
                                                          • 2l: Container from Container
                                                          • 2m: Container from Noun
                                                          • 2n: Functional Hacks
                                                          • 2o: Normalizing Containers
                                                          • 2p: Serialization
                                                          • 2q: Molds and Mold-Builders
                                                          • 3a: Modular and Signed Ints
                                                          • 3b: Floating Point
                                                          • 3c: Urbit Time
                                                          • 3d: SHA Hash Family
                                                          • 3e: AES encryption (Removed)
                                                          • 3f: Scrambling
                                                          • 3g: Molds and Mold-Builders
                                                          • 4a: Exotic Bases
                                                          • 4b: Text Processing
                                                          • 4c: Tank Printer
                                                          • 4d: Parsing (Tracing)
                                                          • 4e: Parsing (Combinators)
                                                          • 4f: Parsing (Rule-Builders)
                                                          • 4g: Parsing (Outside Caller)
                                                          • 4h: Parsing (ASCII Glyphs)
                                                          • 4i: Parsing (Useful Idioms)
                                                          • 4j: Parsing (Bases and Base Digits)
                                                          • 4k: Atom Printing
                                                          • 4l: Atom Parsing
                                                          • 4m: Formatting Functions
                                                          • 4n: Virtualization
                                                          • 4o: Molds
                                                          • 5a: Compiler Utilities
                                                          • 5b: Macro Expansion
                                                          • 5c: Compiler Backend & Prettyprinter
                                                          • 5d: Parser
                                                          • 5e: Molds and mold builders
                                                          • 5f: Profiling support
                                                          • Zuse

                                                            • Table of Contents
                                                            • 2d(1-5): To JSON, Wains
                                                            • 2d(6): From JSON
                                                            • 2d(7): From JSON (unit)
                                                            • 2e(2-3): Print & Parse JSON
                                                        • Nock

                                                          • Nock Definition
                                                          • Explanation
                                                          • Example
                                                          • Implementations
                                                          • Vere

                                                            • C Runtime System
                                                            • Land of Nouns
                                                            • API overview by prefix
                                                            • C in Urbit
                                                            • Writing Jets
                                                            • Cryptography
                                                            • Azimuth

                                                              • Overview
                                                              • Urbit HD Wallet
                                                              • Azimuth Data Flow
                                                              • Azimuth.eth
                                                              • Ecliptic.eth
                                                              • Advanced Azimuth Tools
                                                              • Life and Rift
                                                              • Layer 2

                                                                • Layer 2 Overview
                                                                • Layer 2 Actions
                                                                • Transaction Format
                                                                • Rollers
                                                                • Roller HTTP RPC-API
                                                                • Custom Roller Tutorial
                                                              • Glossary

                                                                • Ames
                                                                • Aqua
                                                                • Arm
                                                                • Arvo
                                                                • Atom
                                                                • Azimuth
                                                                • Battery
                                                                • Behn
                                                                • Bridge
                                                                • Censures
                                                                • Ceremony
                                                                • chat
                                                                • Claims
                                                                • Clay
                                                                • Comet
                                                                • Core
                                                                • Delegated Sending
                                                                • Desk
                                                                • Dill
                                                                • Document Proposal
                                                                • Dojo
                                                                • Door
                                                                • Ecliptic
                                                                • Event Log
                                                                • Eyre
                                                                • Ford
                                                                • Galaxy
                                                                • Gall
                                                                • Gate
                                                                • HD Wallet
                                                                • Hoon
                                                                • Invite Tree
                                                                • Iris
                                                                • Jael
                                                                • Jaque
                                                                • Keyfile
                                                                • Landscape
                                                                • Mark
                                                                • Moon
                                                                • Nock
                                                                • Noun
                                                                • OTA Updates
                                                                • Payload
                                                                • pH
                                                                • Pier
                                                                • Pill
                                                                • Planet
                                                                • Proxies
                                                                • Replay
                                                                • Factory Reset
                                                                • Naive rollups
                                                                • Sail/Udon
                                                                • Senate
                                                                • Ship
                                                                • ship.arvo.network
                                                                • Star
                                                                • |sync
                                                                • Trap
                                                                • Upgrade Proposal
                                                                • Vane
                                                                • Vere
                                                                • Voting
                                                                • Wallet-Generator
                                                                Urbit
                                                                • Introduction
                                                                • Development

                                                                  • Getting Started
                                                                  • Environment Setup
                                                                  • Grants Program
                                                                  • Project Repositories
                                                                  • Precepts
                                                                  • System Overview

                                                                    • Arvo
                                                                    • Hoon
                                                                    • Nock
                                                                    • Vere
                                                                    • Azimuth
                                                                    • Cryptography
                                                                    • Arvo

                                                                      • Overview
                                                                      • Ames

                                                                        • Overview
                                                                        • Cryptography
                                                                        • API Reference
                                                                        • Scry Reference
                                                                        • Data Types
                                                                        • Behn

                                                                          • Overview
                                                                          • API Reference
                                                                          • Scry Reference
                                                                          • Examples
                                                                          • Clay

                                                                            • Overview
                                                                            • Architecture
                                                                            • Using Clay
                                                                            • Data Types
                                                                            • Scry Reference
                                                                            • API Reference
                                                                            • Examples
                                                                            • Marks

                                                                              • Overview
                                                                              • Writing Marks
                                                                              • Using Marks
                                                                              • Examples
                                                                            • Dill

                                                                              • Overview
                                                                              • API Reference
                                                                              • Scry Reference
                                                                              • Data Types
                                                                              • Eyre

                                                                                • Overview
                                                                                • External API Reference
                                                                                • Internal API Reference
                                                                                • Scry Reference
                                                                                • Data Types
                                                                                • Guide
                                                                                • Ford

                                                                                  • Overview
                                                                                  • Gall

                                                                                    • Overview
                                                                                    • API Reference
                                                                                    • Data Types
                                                                                    • Iris

                                                                                      • Overview
                                                                                      • API Reference
                                                                                      • Data Types
                                                                                      • Example
                                                                                      • Jael

                                                                                        • Overview
                                                                                        • API Reference
                                                                                        • Scry Reference
                                                                                        • Data Types
                                                                                        • Examples
                                                                                        • Concepts

                                                                                          • Scries
                                                                                          • Subscriptions
                                                                                          • Tutorials

                                                                                            • Move Trace
                                                                                            • Reference

                                                                                              • Cryptography
                                                                                              • Filesystem Hierarchy
                                                                                            • Userspace

                                                                                              • Overview
                                                                                              • HTTP API Guide
                                                                                              • Gall Guide

                                                                                                • Introduction
                                                                                                • 1. Arvo
                                                                                                • 2. The Agent Core
                                                                                                • 3. Imports and Aliases
                                                                                                • 4. Lifecycle
                                                                                                • 5. Cards
                                                                                                • 6. Pokes
                                                                                                • 7. Structures and Marks
                                                                                                • 8. Subscriptions
                                                                                                • 9. Vanes
                                                                                                • 10. Scries
                                                                                                • 11. Failure
                                                                                                • 12. Next Steps
                                                                                                • Appendix: Types
                                                                                                • Full-Stack Walkthrough

                                                                                                  • 1. Introduction
                                                                                                  • 2. Types
                                                                                                  • 3. Agent
                                                                                                  • 4. JSON
                                                                                                  • 5. Marks
                                                                                                  • 6. Eyre
                                                                                                  • 7. React app setup
                                                                                                  • 8. React app logic
                                                                                                  • 9. Desk and glob
                                                                                                  • 10. Summary
                                                                                                  • Graph Store

                                                                                                    • Graph Store Overview
                                                                                                    • Data Structure Overview
                                                                                                    • Validator Walkthrough
                                                                                                    • Sample Application: Library
                                                                                                    • Graph Store - Reference
                                                                                                    • Advanced Info
                                                                                                    • Threads

                                                                                                      • Overview
                                                                                                      • HTTP API
                                                                                                      • Reference
                                                                                                      • Basics

                                                                                                        • Fundamentals
                                                                                                        • Bind
                                                                                                        • Input
                                                                                                        • Output
                                                                                                        • Summary
                                                                                                        • Gall

                                                                                                          • Start Thread
                                                                                                          • Take Result
                                                                                                          • Take Facts
                                                                                                          • Stop Thread
                                                                                                          • Poke Thread
                                                                                                          • Examples

                                                                                                            • Fetch JSON
                                                                                                            • Child Thread
                                                                                                            • Main-loop
                                                                                                            • Poke Agent
                                                                                                            • Scry
                                                                                                            • Take Fact
                                                                                                          • Distribution

                                                                                                            • Overview
                                                                                                            • Guide
                                                                                                            • Docket File
                                                                                                            • Glob
                                                                                                            • Dojo Tools
                                                                                                          • Hoon

                                                                                                            • Overview
                                                                                                            • Hoon School

                                                                                                              • 1.1 Introduction
                                                                                                              • 1.1.1 Walkthrough: List of Numbers
                                                                                                              • 1.2 Nouns
                                                                                                              • 1.3 Hoon Syntax
                                                                                                              • 1.3.1 Walkthrough: Conditionals
                                                                                                              • 1.4 Gates (Hoon Functions)
                                                                                                              • 1.4.1 Walkthrough: Recursion
                                                                                                              • 1.5 Lists
                                                                                                              • 1.5.1 Walkthrough: Fibonacci Sequence
                                                                                                              • 1.6 The Subject and Its Legs
                                                                                                              • 1.6.1 Walkthrough: Ackermann Function
                                                                                                              • 1.7 Arms and Cores
                                                                                                              • 1.7.1 Walkthrough: Caesar Cipher
                                                                                                              • 1.8 Doors
                                                                                                              • 1.8.1 Bank Account
                                                                                                              • 1.9 Generators
                                                                                                              • 2.1 Atoms, Auras, and Simple Cell Types
                                                                                                              • 2.2 Type Checking and Type Inference
                                                                                                              • 2.3 Structures and Complex Types
                                                                                                              • 2.3.1 Walkthrough: Libraries
                                                                                                              • 2.3.2 Molds
                                                                                                              • 2.4 Standard Library: Trees, Sets, and Maps
                                                                                                              • 2.5 Type Polymorphism
                                                                                                              • 2.5.1 Walkthrough: Iron Polymorphism and Wet Polymorphism
                                                                                                              • 2.5.2 Walkthrough: Lead Polymorphism
                                                                                                              • 2.6 Behn
                                                                                                              • 2.7 Gall
                                                                                                              • 2.7.1 Gall Walkthrough: Egg Timer
                                                                                                              • Guides

                                                                                                                • CLI apps
                                                                                                                • Parsing
                                                                                                                • JSON
                                                                                                                • Strings
                                                                                                                • Sail (HTML)
                                                                                                                • Writing Aqua Tests
                                                                                                                • Reference

                                                                                                                  • Cheat Sheet
                                                                                                                  • Irregular forms
                                                                                                                  • Hoon Errors
                                                                                                                  • Hoon Style Guide
                                                                                                                  • Basic Types
                                                                                                                  • Advanced Types
                                                                                                                  • Auras
                                                                                                                  • Runes

                                                                                                                    • Atoms and strings
                                                                                                                    • Nock . ('dot')
                                                                                                                    • Wild ! ('zap')
                                                                                                                    • Change Subject = ('tis')
                                                                                                                    • Conditionals ? ('wut')
                                                                                                                    • Cores | ('bar')
                                                                                                                    • Arms + ('lus')
                                                                                                                    • Cells : ('col')
                                                                                                                    • Calls % ('cen')
                                                                                                                    • Casts ^ ('ket')
                                                                                                                    • Structures $ ('buc')
                                                                                                                    • Make ; ('mic')
                                                                                                                    • Hints ~ ('sig')
                                                                                                                    • Imports / ('fas')
                                                                                                                    • Terminators -- and ==
                                                                                                                    • Limbs and wings

                                                                                                                      • Limbs
                                                                                                                      • Wings
                                                                                                                      • Standard library

                                                                                                                        • Table of Contents
                                                                                                                        • 1a: Basic Arithmetic
                                                                                                                        • 1b: Tree Addressing
                                                                                                                        • 1c: Molds and Mold-Builders
                                                                                                                        • 2a: Unit Logic
                                                                                                                        • 2b: List Logic
                                                                                                                        • 2c: Bit Arithmetic
                                                                                                                        • 2d: Bit Logic
                                                                                                                        • 2e: Insecure Hashing
                                                                                                                        • 2f: Noun Ordering
                                                                                                                        • 2g: Unsigned Powers
                                                                                                                        • 2h: Set Logic
                                                                                                                        • 2i: Map Logic
                                                                                                                        • 2j: Jar and Jug Logic
                                                                                                                        • 2k: Queue Logic
                                                                                                                        • 2l: Container from Container
                                                                                                                        • 2m: Container from Noun
                                                                                                                        • 2n: Functional Hacks
                                                                                                                        • 2o: Normalizing Containers
                                                                                                                        • 2p: Serialization
                                                                                                                        • 2q: Molds and Mold-Builders
                                                                                                                        • 3a: Modular and Signed Ints
                                                                                                                        • 3b: Floating Point
                                                                                                                        • 3c: Urbit Time
                                                                                                                        • 3d: SHA Hash Family
                                                                                                                        • 3e: AES encryption (Removed)
                                                                                                                        • 3f: Scrambling
                                                                                                                        • 3g: Molds and Mold-Builders
                                                                                                                        • 4a: Exotic Bases
                                                                                                                        • 4b: Text Processing
                                                                                                                        • 4c: Tank Printer
                                                                                                                        • 4d: Parsing (Tracing)
                                                                                                                        • 4e: Parsing (Combinators)
                                                                                                                        • 4f: Parsing (Rule-Builders)
                                                                                                                        • 4g: Parsing (Outside Caller)
                                                                                                                        • 4h: Parsing (ASCII Glyphs)
                                                                                                                        • 4i: Parsing (Useful Idioms)
                                                                                                                        • 4j: Parsing (Bases and Base Digits)
                                                                                                                        • 4k: Atom Printing
                                                                                                                        • 4l: Atom Parsing
                                                                                                                        • 4m: Formatting Functions
                                                                                                                        • 4n: Virtualization
                                                                                                                        • 4o: Molds
                                                                                                                        • 5a: Compiler Utilities
                                                                                                                        • 5b: Macro Expansion
                                                                                                                        • 5c: Compiler Backend & Prettyprinter
                                                                                                                        • 5d: Parser
                                                                                                                        • 5e: Molds and mold builders
                                                                                                                        • 5f: Profiling support
                                                                                                                        • Zuse

                                                                                                                          • Table of Contents
                                                                                                                          • 2d(1-5): To JSON, Wains
                                                                                                                          • 2d(6): From JSON
                                                                                                                          • 2d(7): From JSON (unit)
                                                                                                                          • 2e(2-3): Print & Parse JSON
                                                                                                                      • Nock

                                                                                                                        • Nock Definition
                                                                                                                        • Explanation
                                                                                                                        • Example
                                                                                                                        • Implementations
                                                                                                                        • Vere

                                                                                                                          • C Runtime System
                                                                                                                          • Land of Nouns
                                                                                                                          • API overview by prefix
                                                                                                                          • C in Urbit
                                                                                                                          • Writing Jets
                                                                                                                          • Cryptography
                                                                                                                          • Azimuth

                                                                                                                            • Overview
                                                                                                                            • Urbit HD Wallet
                                                                                                                            • Azimuth Data Flow
                                                                                                                            • Azimuth.eth
                                                                                                                            • Ecliptic.eth
                                                                                                                            • Advanced Azimuth Tools
                                                                                                                            • Life and Rift
                                                                                                                            • Layer 2

                                                                                                                              • Layer 2 Overview
                                                                                                                              • Layer 2 Actions
                                                                                                                              • Transaction Format
                                                                                                                              • Rollers
                                                                                                                              • Roller HTTP RPC-API
                                                                                                                              • Custom Roller Tutorial
                                                                                                                            • Glossary

                                                                                                                              • Ames
                                                                                                                              • Aqua
                                                                                                                              • Arm
                                                                                                                              • Arvo
                                                                                                                              • Atom
                                                                                                                              • Azimuth
                                                                                                                              • Battery
                                                                                                                              • Behn
                                                                                                                              • Bridge
                                                                                                                              • Censures
                                                                                                                              • Ceremony
                                                                                                                              • chat
                                                                                                                              • Claims
                                                                                                                              • Clay
                                                                                                                              • Comet
                                                                                                                              • Core
                                                                                                                              • Delegated Sending
                                                                                                                              • Desk
                                                                                                                              • Dill
                                                                                                                              • Document Proposal
                                                                                                                              • Dojo
                                                                                                                              • Door
                                                                                                                              • Ecliptic
                                                                                                                              • Event Log
                                                                                                                              • Eyre
                                                                                                                              • Ford
                                                                                                                              • Galaxy
                                                                                                                              • Gall
                                                                                                                              • Gate
                                                                                                                              • HD Wallet
                                                                                                                              • Hoon
                                                                                                                              • Invite Tree
                                                                                                                              • Iris
                                                                                                                              • Jael
                                                                                                                              • Jaque
                                                                                                                              • Keyfile
                                                                                                                              • Landscape
                                                                                                                              • Mark
                                                                                                                              • Moon
                                                                                                                              • Nock
                                                                                                                              • Noun
                                                                                                                              • OTA Updates
                                                                                                                              • Payload
                                                                                                                              • pH
                                                                                                                              • Pier
                                                                                                                              • Pill
                                                                                                                              • Planet
                                                                                                                              • Proxies
                                                                                                                              • Replay
                                                                                                                              • Factory Reset
                                                                                                                              • Naive rollups
                                                                                                                              • Sail/Udon
                                                                                                                              • Senate
                                                                                                                              • Ship
                                                                                                                              • ship.arvo.network
                                                                                                                              • Star
                                                                                                                              • |sync
                                                                                                                              • Trap
                                                                                                                              • Upgrade Proposal
                                                                                                                              • Vane
                                                                                                                              • Vere
                                                                                                                              • Voting
                                                                                                                              • Wallet-Generator
                                                                                                                              Urbit/Documentation/Userspace/Threads/Examples

                                                                                                                              Fetch JSON

                                                                                                                              Grabbing JSON from some url is very easy.

                                                                                                                              strandio includes the fetch-json function which will handle the HTTP request, response, and parsing, producing json.

                                                                                                                              The following thread fetches the current Bitcoin price from the CoinGecko API in the specified currency and prints it to the terminal.

                                                                                                                              btc-price.hoon

                                                                                                                              /-  spider
                                                                                                                              /+  *strandio
                                                                                                                              =,  strand=strand:spider
                                                                                                                              =,  dejs-soft:format
                                                                                                                              =,  strand-fail=strand-fail:libstrand:spider
                                                                                                                              ^-  thread:spider
                                                                                                                              |=  arg=vase
                                                                                                                              =/  m  (strand ,vase)
                                                                                                                              ^-  form:m
                                                                                                                              =/  url
                                                                                                                                "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies="
                                                                                                                              =/  cur  !<((unit @tas) arg)
                                                                                                                              ?~  cur  (strand-fail %no-arg ~)
                                                                                                                              =.  u.cur  (crip (cass (trip u.cur)))
                                                                                                                              ?.  ((sane %tas) u.cur)  (strand-fail %bad-currency-format ~)
                                                                                                                              ;<  =json  bind:m  (fetch-json (weld url (trip u.cur)))
                                                                                                                              =/  price=(unit @ta)  ((ot ~[bitcoin+(ot [u.cur no]~)]) json)
                                                                                                                              ?~  price  ((slog 'Currency not found.' ~) (pure:m !>(~)))
                                                                                                                              %-  (slog leaf+"{(trip u.price)} {(cuss (trip u.cur))}" ~)
                                                                                                                              (pure:m !>(~))
                                                                                                                              

                                                                                                                              Save it as /ted/btc-price.hoon in the %base desk of a fake ship, |commit %base and run it with -btc-price %usd. You should see something like:

                                                                                                                              > -btc-price %usd
                                                                                                                              49168 USD

                                                                                                                              You can try with other currencies as well:

                                                                                                                              > -btc-price %nzd
                                                                                                                              72455 NZD
                                                                                                                              > -btc-price %aud
                                                                                                                              68866 AUD
                                                                                                                              > -btc-price %gbp
                                                                                                                              37319 GBP

                                                                                                                              Analysis

                                                                                                                              The thread takes an @tas as its argument, which the dojo wraps in a unit. We extract the vase and check it's not empty:

                                                                                                                              =/  cur  !<((unit @tas) arg)
                                                                                                                              ?~  cur  (strand-fail %no-arg ~)
                                                                                                                              

                                                                                                                              We then convert it to lowercase and check it's a valid @tas:

                                                                                                                              =.  u.cur  (crip (cass (trip u.cur)))
                                                                                                                              ?.  ((sane %tas) u.cur)  (strand-fail %bad-currency-format ~)
                                                                                                                              

                                                                                                                              Next, we use the fetch-json function in strandio like so:

                                                                                                                              ;<  =json  bind:m  (fetch-json (weld url (trip u.cur)))
                                                                                                                              

                                                                                                                              We convert the currency to a tape and weld it to the end of the url, which we give as an argument to fetch-json. The fetch-json function will make the request to the URL, receive the result, parse the JSON and produce the result as a json structure.

                                                                                                                              The JSON the API produces looks like:

                                                                                                                              {
                                                                                                                                "bitcoin": {
                                                                                                                                  "usd": 49477
                                                                                                                                }
                                                                                                                              }
                                                                                                                              

                                                                                                                              Since it's an object in an object, we decode them using nested ot:dejs-soft:format functions, and the price itself using no:dejs-soft:format to produce a (unit @ta):

                                                                                                                              =/  price=(unit @ta)  ((ot ~[bitcoin+(ot [u.cur no]~)]) json)
                                                                                                                              

                                                                                                                              Finally, we check if the unit is null and either print an error or print the price to the terminal with slog functions (the thread itself produces ~):

                                                                                                                              ?~  price  ((slog 'Currency not found.' ~) (pure:m !>(~)))
                                                                                                                              %-  (slog leaf+"{(trip u.price)} {(cuss (trip u.cur))}" ~)
                                                                                                                              (pure:m !>(~))
                                                                                                                              

                                                                                                                              For more information about working with json, see the JSON Guide.

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