FlatCityBuf CLI

August 11, 2026 · View on GitHub

A command-line interface for converting between CityJSON and FlatCityBuf (FCB) formats, with support for spatial and attribute indexing.

Installation

cargo install fcb_cli --locked

This installs the fcb binary to your Cargo bin directory (usually ~/.cargo/bin/).

Option 2: Build from Source

# Clone the repository
git clone https://github.com/cityjson/flatcitybuf.git
cd flatcitybuf/src/rust

# Build in release mode
cargo build --release -p fcb_cli

Option 3: Run with Cargo (Development)

cd flatcitybuf/src/rust
cargo run -p fcb_cli -- <command> [args]

# Example: convert CityJSONSeq to FCB
cargo run -p fcb_cli -- ser input.city.jsonl output.fcb

Usage

fcb <COMMAND> [OPTIONS] <INPUT> <OUTPUT>

Input and output are positional: the input comes first, the output second. The read-only command inspect takes a single positional argument.

Commands

ser - Serialize CityJSON to FCB

Convert CityJSON files to FlatCityBuf format with optional indexing.

fcb ser [OPTIONS] <INPUT>... <OUTPUT>

Arguments:

  • <INPUT>... - Input file(s) or glob patterns (supports multiple files; each path must end in .json or .jsonl -- ser does not read from stdin)
  • <OUTPUT> - Output file, always the last positional (use '-' for stdout)

Options:

  • -a, --attr-index ATTRIBUTES - Comma-separated list of attributes to create index for
  • -A, --index-all-attributes - Index all attributes found in the dataset
  • -s, --no-spatial-index - Disable the spatial index (it is written by default)
  • --attr-branching-factor FACTOR - Branching factor for attribute index (default: 16 with --attr-index, 256 with --index-all-attributes)
  • --index-node-size SIZE - Node size of the spatial R-tree index (default: 16)
  • --no-feature-count - Write a features_count of 0, meaning "unknown", which forces readers to scan to EOF (conformance fixtures only)
  • -b, --bbox BBOX - Bounding box filter in format "minx,miny,maxx,maxy"
  • -g, --ge - Automatically calculate and set geospatial extent in header

Examples:

# basic conversion from CityJSONSeq
fcb ser input.city.jsonl output.fcb

# convert CityJSON file (standard .json format)
fcb ser city.city.json output.fcb

# multiple input files -- the last positional is the output
fcb ser file1.city.jsonl file2.city.jsonl merged.fcb

# glob patterns to process all matching files
fcb ser 'data/*.city.jsonl' output.fcb
fcb ser 'cities/**/*.city.json' all_cities.fcb

# with attribute indexing
fcb ser delft.city.jsonl delft_attr.fcb \
  --attr-index identificatie,tijdstipregistratie,b3_is_glas_dak,b3_h_dak_50p \
  --attr-branching-factor 256

# index all attributes
fcb ser data.city.jsonl data.fcb --index-all-attributes

# with bounding box filter
fcb ser large_dataset.city.jsonl filtered.fcb \
  --bbox "4.35,52.0,4.4,52.1"

# to stdout (input must still be a real file path)
fcb ser input.city.jsonl - > output.fcb

deser - Deserialize FCB to CityJSON

Convert FlatCityBuf files back to CityJSON format.

fcb deser <INPUT> <OUTPUT>

Arguments:

  • <INPUT> - Input FCB file (use '-' for stdin)
  • <OUTPUT> - Output file (use '-' for stdout)

Examples:

# basic conversion
fcb deser input.fcb output.city.jsonl

# from stdin to stdout
cat input.fcb | fcb deser - - > output.city.jsonl

inspect - Inspect an FCB file

Show what an FCB dataset's header declares, either in a full-screen terminal UI or as a static text report. Only the header is read -- feature bytes are never fetched -- so inspecting a remote file over HTTP range requests costs a couple of small requests regardless of dataset size.

fcb inspect [--static] <SOURCE>

Arguments:

  • <SOURCE> - Local path or HTTP(S) URL to an FCB file

Options:

  • --static - print the static report instead of the terminal UI

Output mode: with stdout on a terminal you get the interactive UI; with stdout piped or redirected inspect prints the static report and exits 0. --static forces the report even on a terminal, which is what scripts and the just inspect recipe use.

The static report includes:

  • Source (the path or URL) and file size (remote sources report unknown)
  • CityJSON version, title, identifier and reference date, when present
  • Feature count and number of attribute columns
  • Geographical extent (min/max and dimensions), when set
  • Index summary: whether a spatial R-tree is present and its node size, plus the names of the indexed attributes
  • Coordinate reference system (code, version, code string), when set
  • Coordinate transform (scale and translate), when present

Tabs (terminal UI):

  • Metadata - version, feature count, index sizes, extent, transform, CRS
  • Columns - the header attribute schema, one row per column
  • Map - the dataset extent drawn on a world map; shown only for a geographic CRS, otherwise the projected extent is printed instead

Key bindings:

  • q, Esc, Ctrl-C - quit
  • Tab, →, l - next tab
  • Shift-Tab, ←, h - previous tab
  • ↓, j / ↑, k - scroll the column list
  • g / G - jump to the first / last column

Examples:

# local file
fcb inspect delft.fcb

# remote file over HTTP range requests -- only the header is fetched
fcb inspect https://example.com/data.fcb

# static report, for scripts and captured output
fcb inspect --static delft.fcb

No terminal, no problem. The terminal UI needs an interactive TTY, so with stdout redirected or piped inspect falls back to the static report and exits 0. Pass --static to get that same report on a terminal; both paths print byte-identical, colour-free text.

cbor - Convert CityJSON to CBOR

Convert CityJSON to Concise Binary Object Representation format.

fcb cbor <INPUT> <OUTPUT>

bson - Convert CityJSON to BSON

Convert CityJSON to Binary JSON format.

fcb bson <INPUT> <OUTPUT>

Format Support

Input Formats

  • CityJSON (.city.json) - Standard CityJSON files
  • CityJSON Text Sequences (.city.jsonl) - Line-delimited CityJSON features
  • FCB (.fcb) - FlatCityBuf binary format

Remote Input: inspect also accepts an http:// or https:// URL and reads the header over HTTP range requests. The other commands (ser, deser, cbor, bson) take local paths only, plus - for stdin/stdout where documented.

Multi-file Support: The ser command accepts multiple input files and glob patterns; the last positional argument is always the output. When merging files with different coordinate transforms, vertices are automatically aligned to the first file's transform.

Output Formats

  • FCB (.fcb) - FlatCityBuf binary format with optional indexing
  • CityJSON Text Sequences (.city.jsonl) - Line-delimited CityJSON features
  • CBOR - Concise Binary Object Representation
  • BSON - Binary JSON

Examples Workflow

# 1. convert cityjson to fcb with attribute indexing
fcb ser dataset.city.jsonl dataset.fcb \
  --attr-index "building_type,height,year_built" \
  --attr-branching-factor 256

# 2. check file information
fcb inspect --static dataset.fcb

# 3. convert back to cityjson
fcb deser dataset.fcb output.city.jsonl

# 4. filter by bounding box and index all attributes
fcb ser large_city.city.jsonl filtered_city.fcb \
  --bbox "4.35,52.0,4.4,52.1" \
  --index-all-attributes

Error Handling

The CLI provides detailed error messages for common issues:

  • Invalid file formats
  • Missing input files
  • Malformed bounding box coordinates
  • Memory limitations for large datasets

License

MIT License - see LICENSE file for details.