Quick Start

This guide will help you get started with OctoFHIR FHIRPath quickly using the CLI tool.

Prerequisites

Make sure you have installed the CLI tool:

cargo install --path fhirpath-cli

Basic Usage

Evaluate FHIRPath Expressions

The most common use case is evaluating FHIRPath expressions against FHIR resources.

# Evaluate an expression against a FHIR resource
octofhir-fhirpath eval "Patient.name.given" patient.json

# Specify output format
octofhir-fhirpath eval "Patient.name.given" patient.json --format json
octofhir-fhirpath eval "Patient.name.given" patient.json --format pretty

Validate FHIRPath Expressions

You can also validate FHIRPath expression syntax:

# Check if an expression is syntactically valid
octofhir-fhirpath validate "Patient.name.given"
octofhir-fhirpath validate "Patient.invalid..syntax"

Example FHIR Resource

Create a sample patient.json file to test with:

{
  "resourceType": "Patient",
  "id": "example",
  "name": [
    {
      "use": "official",
      "family": "Smith",
      "given": ["John", "Michael"]
    }
  ],
  "gender": "male",
  "birthDate": "1990-01-01"
}

Common FHIRPath Expressions

Try these expressions with your sample patient:

# Get the resource type
octofhir-fhirpath eval "resourceType" patient.json

# Get the patient's family name
octofhir-fhirpath eval "name.family" patient.json

# Get all given names
octofhir-fhirpath eval "name.given" patient.json

# Get the first given name
octofhir-fhirpath eval "name.given[0]" patient.json

# Get the gender
octofhir-fhirpath eval "gender" patient.json

# Get names with official use
octofhir-fhirpath eval "name.where(use = 'official')" patient.json

Output Formats

OctoFHIR FHIRPath supports different output formats:

Pretty Format (Default)

octofhir-fhirpath eval "name.given" patient.json --format pretty

Output:

["John", "Michael"]

JSON Format

octofhir-fhirpath eval "name.given" patient.json --format json

Output:

["John", "Michael"]

Next Steps

• Learn more about CLI usage
• Explore usage examples
• Integrate with Rust or Node.js
• Read the FHIRPath specification