cbor

A command-line tool for encoding and decoding CBOR (Concise Binary Object Representation, RFC 8949) using serde. Convert between CBOR and JSON, YAML, and TOML, inspect the contents of CBOR files, and pipe it all through standard Unix tools.

CBOR is a compact binary data format with a data model close to JSON's but with smaller payloads, richer types (byte strings, bignums, tags), and fast binary parsing. cbor makes working with it as easy as jq/yq make working with their formats.

Why

• Pipe-friendly. Reads files or stdin, writes stdout. Composes with cat, curl, grep, and friends.
• Multi-format. Convert JSON, YAML, TOML, and CBOR freely — all four directions.
• Streaming. Handles arbitrarily long inputs one item at a time, and supports CBOR sequences (multiple concatenated items in one stream, RFC 8742).
• Schema-less. Works on any data via serde's dynamic Value type. No structs, no setup.
• Deep inspection. Renders CBOR in Concise Diagnostic Notation (RFC 8949 §8) — human-readable, standard, and CBOR-aware (byte strings, tags, bignums).
• Delimiters. Custom output delimiters for joining multiple items.

Installation

Homebrew

brew tap ironspecs/cbor
brew install cbor-cli

Cargo

cargo install cbor-cli

Debian

Installs the public key, downloads the latest .deb file, and installs it:

curl -sSL https://raw.githubusercontent.com/ironspecs/cbor-cli/main/install-cbor-deb.sh | sh

Build from source

git clone https://github.com/ironspecs/cbor-cli
cd cbor-cli
cargo build --release
# Binary is at target/release/cbor

Usage

The three subcommands are designed to chain:

import   convert JSON/YAML/TOML/CBOR  ->  CBOR
export   convert CBOR                 ->  JSON/YAML/TOML/CBOR
inspect  render CBOR                  ->  Concise Diagnostic Notation

Import (encode to CBOR)

cbor import data.json > data.cbor

Format is auto-detected from the file extension (.json, .yaml, .yml, .toml). To force it, or when reading from stdin:

cat data.json | cbor import --format=json > data.cbor

Export (decode from CBOR)

cbor export --format=json data.cbor > data.json

# Pretty-printed JSON
cbor export --format=json --pretty data.cbor

Convert between formats

Because both commands stream, you can chain them to convert any format to any other through CBOR as an intermediate:

# JSON -> YAML
cbor import data.json | cbor export --format=yaml > data.yaml

# YAML -> TOML
cbor import data.yaml | cbor export --format=toml > data.toml

Inspect (debug)

inspect renders each CBOR item in Concise Diagnostic Notation — a human-readable form that preserves CBOR-specific details JSON debug output would lose, like byte strings:

$ cbor import data.json | cbor inspect
{"name": "cbor", "types": [1, 2, 3]}

Inspect a CBOR file directly:

cbor inspect data.cbor

CDN distinguishes CBOR types that JSON can't represent:

CBOR type	CDN output
Byte string	h'0102'
Tagged unsigned bignum	16909060
Integer	42
Text string	"hello"
Array	[1, 2, 3]
Map	{"a": "b"}
Null	null
Boolean	true / false

Multiple files and streams

Pass multiple files; each is processed in turn:

cbor import a.json b.json > combined.cbor

Concatenated items from stdin are supported too — useful for CBOR sequences and for joining multiple JSON documents:

cat a.json b.json | cbor import --format=json > combined.cbor

Custom delimiters

When exporting multiple items, join them with a custom delimiter. The default is \n (for YAML, the document separator ---):

# Comma-separated JSON values
cbor export --format=json --delimiter=',' data.cbor

# Shorthand
cbor -d=',' export data.cbor

The escapes \n and \t are interpreted literally.

Full reference

cbor [OPTIONS] [COMMAND]

Commands:
  inspect  Deep inspection of CBOR files, for debugging, learning, or repairing
  import   Convert a file of some other type to CBOR
  export   Convert CBOR files to some other type
  help     Print help for a command

Options:
  -v, --verbose...             Increase verbosity (repeatable)
  -d, --delimiter <DELIMITER>  Delimiter between multiple output items
  -h, --help                   Print help
  -V, --version                Print version

Each subcommand has its own --help:

cbor import --help
cbor export --help
cbor inspect --help

Library

The core conversion functions are exposed as a library, in case you want to embed them in another Rust project:

use cbor_cli::import::import_from_reader;

// Convert a JSON stream to CBOR.
let json = br#"{"key": "value"}"#;
let mut cbor = Vec::new();
import_from_reader("json", &json[..], &mut cbor).unwrap();

Library functions return anyhow::Result, so errors propagate naturally:

use anyhow::Context;
use cbor_cli::export::export_from_reader;

export_from_reader("json", "\n", false, &cbor[..], &mut writer)
    .context("Failed to export data.cbor")?;

See the src/ modules for the full API surface:

Module	Purpose
import	Encode JSON/YAML/TOML/CBOR streams to CBOR
export	Decode CBOR streams to JSON/YAML/TOML/CBOR
inspect	Render CBOR as Concise Diagnostic Notation
files	Path helpers: format detection, existence checks
config	CLI definition (clap)

Standards

• RFC 8949 — Concise Binary Object Representation
• RFC 8742 — CBOR Sequences (concatenated items in one stream)
• RFC 8949 §8 — Concise Diagnostic Notation

Development

cargo test      # run the test suite
cargo clippy    # lints
cargo fmt       # formatting
cargo run --    # build and run in one step

Examples of every supported conversion are in examples/test.sh.

Building release packages

Cross-compilation and Debian packaging are configured in .github/workflows/rust_build.yml. Local .deb build:

cargo install cargo-deb
rustup target add i686-unknown-linux-gnu
cargo deb --target=i686-unknown-linux-gnu

License

Apache-2.0. See LICENSE.