flatc - Man Page

flatc [OPTION]... FILE... [-- BINARY_FILE...]

FILEs may be schemas (must end in .fbs), binary schemas (must end in .bfbs), or JSON files (conforming to preceding schema). BINARY_FILEs after the -- must be binary flatbuffer format files.

Output files are named using the base file name of the input, and written to the current directory or the path given by -o.

-b,  --binary

Generate wire format binaries for any data definitions.

-c,  --cpp

Generate C++ headers for tables/structs.

-n,  --csharp

Generate C# classes for tables/structs.

-d,  --dart

Generate Dart classes for tables/structs.

-g,  --go

Generate Go files for tables/structs.

-j,  --java

Generate Java classes for tables/structs.

-t,  --json

Generate text output for any data definitions.

--jsonschema

Generate Json schema.

--kotlin

Generate Kotlin classes for tables/structs.

--kotlin-kmp

Generate Kotlin multiplatform classes for tables/structs.

--lobster

Generate Lobster files for tables/structs.

-l,  --lua

Generate Lua files for tables/structs.

--nim

Generate Nim files for tables/structs.

--php

Generate PHP files for tables/structs.

--proto

Input is a .proto, translate to .fbs.

-p,  --python

Generate Python files for tables/structs.

-r,  --rust

Generate Rust files for tables/structs.

--swift

Generate Swift files for tables/structs.

-T,  --ts

Generate TypeScript code for tables/structs.

-o PATH

Prefix PATH to all generated files.

-I PATH

Search for includes in the specified path.

-M

Print make(1) rules for generated files.

--version

Print the version number of flatc and exit.

-h,  --help

Print help text and exit.

--strict-json

Strict JSON: field names must be / will be quoted, no trailing commas in tables/vectors.

--allow-non-utf8

Pass non-UTF-8 input through parser and emit nonstandard \x escapes in JSON. (Default is to raise parse error on non-UTF-8 input.)

--natural-utf8

Output strings with UTF-8 as human-readable strings. By default, UTF-8 characters are printed as \uXXXX escapes.

--defaults-json

Output fields whose value is the default when writing JSON.

--unknown-json

Allow fields in JSON that are not defined in the schema. These fields will be discarded when generating binaries.

--no-prefix

Don’t prefix enum values with the enum type in C++.

--scoped-enums

Use C++11 style scoped and strongly typed enums. Also implies --no-prefix.

--no-emit-min-max-enum-values

Disable generation of MIN and MAX enumerated values for scoped enums and prefixed enums.

--swift-implementation-only

Adds a @_implementationOnly to Swift imports.

--gen-includes

(deprecated), this is the default behavior. If the original behavior is required (no include statements) use --no-includes.

--no-includes

Don’t generate include statements for included schemas the generated file depends on (C++, Python, Proto-to-Fbs).

--gen-mutable

Generate accessors that can mutate buffers in-place.

--gen-onefile

Generate single output file for C#, Go, Java, Kotlin and Python. Implies --no-include.

--gen-name-strings

Generate type name functions for C++ and Rust.

--gen-object-api

Generate an additional object-based API.

--gen-compare

Generate operator== for object-based API types.

--gen-nullable

Add Clang _Nullable for C++ pointer or @Nullable for Java.

--java-package-prefix

Add a prefix to the generated package name for Java.

--java-checkerframework

Add @Pure for Java.

--gen-generated

Add @Generated annotation for Java

--gen-jvmstatic

Add @JvmStatic annotation for Kotlin methods in companion object for interop from Java to Kotlin.

--gen-all

Generate not just code for the current schema files, but for all files it includes as well. If the language uses a single file for output (by default the case for C++ and JS), all code will end up in this one file.

--gen-json-emit

Generates encoding code which emits Flatbuffers into JSON.

--cpp-include

Adds an #include in generated file.

--cpp-ptr-type T

Set object API pointer type (default std::unique_ptr).

--cpp-str-type T

Set object API string type (default std::string). T::c_str(), T::length(), and T::empty() must be supported. The custom type also needs to be constructible from std::string (see the --cpp-str-flex-ctor option to change this behavior).

--cpp-str-flex-ctor

Don’t construct custom string types by passing std::string from Flatbuffers, but (char* + length).

--cpp-field-case-style STYLE

Generate C++ fields using selected case style. Supported STYLE values:

• unchanged – leave unchanged (default)
• upper – schema snake_case emits UpperCamel
• lower – schema snake_case emits lowerCamel

--cpp-std CPP_STD

Generate a C++ code using features of selected C++ standard.

Supported CPP_STD values:

• c++0x – generate code compatible with old compilers;
• c++11 – use C++11 code generator (default);
• c++17 – use C++17 features in generated code (experimental).

--cpp-static-reflection

When using C++17, generate extra code to provide compile-time (static) reflection of Flatbuffers types. Requires --cpp-std to be “c++17” or higher.

--object-prefix PREFIX

Customise class prefix for C++ object-based API.

--object-suffix SUFFIX

Customise class suffix for C++ object-based API. Default value is “T”.

--go-namespace

Generate the overriding namespace in Golang.

--go-import IMPORT

Generate the overriding import for flatbuffers in Golang (default is “github.com/google/flatbuffers/go”).

--go-module-name

Prefix local import paths of generated go code with the module name.

--raw-binary

Allow binaries without file_identifier to be read. This may crash flatc given a mismatched schema.

--size-prefixed

Input binaries are size prefixed buffers.

--proto-namespace-suffix SUFFIX

Add this namespace to any flatbuffers generated from protobufs.

--oneof-union

Translate .proto oneofs to flatbuffer unions.

--keep-proto-id

Keep protobuf field ids in generated fbs file.

--proto-id-gap

Action that should be taken when a gap between protobuf ids found.

Supported values:

• nop – do not care about gap
• warn – A warning message will be shown about the gap in protobuf ids (default)
• error – An error message will be shown and the fbs generation will be interrupted.

--grpc

Generate GRPC interfaces for the specified languages.

--schema

Serialize schemas instead of JSON (use with -b).

--bfbs-filenames PATH

Sets the root path where reflection filenames in reflection.fbs are relative to. The root is denoted with //. E.g. if PATH=/a/b/c then /a/d/e.fbs will be serialized as //../d/e.fbs. (PATH defaults to the directory of the first provided schema file.

--bfbs-absolute-paths

Uses absolute paths instead of relative paths in the BFBS output.

--bfbs-comments

Add doc comments to the binary schema files.

--bfbs-builtins

Add builtin attributes to the binary schema files.

--bfbs-gen-embed

Generate code to embed the bfbs schema to the source.

--conform FILE

Specify a schema the following schemas should be an evolution of. Gives errors if not.

--conform-includes

Include path for the schema given with --conform PATH.

--filename-suffix SUFFIX

The suffix appended to the generated file names. Default is _generated.

--filename-ext EXT

The extension appended to the generated file names. Default is language-specific (e.g., .h for C++)

--include-prefix PATH

Prefix this PATH to any generated include statements.

--keep-prefix

Keep original prefix of schema include statement.

--reflect-types

Add minimal type reflection to code generation.

--reflect-names

Add minimal type/name reflection.

--rust-serialize

Implement serde::Serialize on generated Rust types.

--rust-module-root-file

Generate Rust code in individual files with a module root file.

--root-type T

Select or override the default root_type.

--require-explicit-ids

When parsing schemas, require explicit ids (id: x).

--force-defaults

Emit default values in binary output from JSON.

--force-empty

When serializing from object API representation, force strings and vectors to empty rather than null.

--force-empty-vectors

When serializing from object API representation, force vectors to empty rather than null.

--flexbuffers

Used with “binary” and “json” options, it generates data using schema-less FlexBuffers.

--no-warnings

Inhibit all warning messages.

--warnings-as-errors

Treat all warnings as errors.

--cs-global-alias

Prepend “global::” to all user-generated csharp classes and structs.

--cs-gen-json-serializer

Allows (de)serialization of JSON text in the Object API. (requires --gen-object-api).

--json-nested-bytes

Allow a nested_flatbuffer field to be parsed as a vector of bytes in JSON, which is unsafe unless checked by a verifier afterwards.

--ts-flat-files

Generate a single typescript file per .fbs file. Implies --ts-entry-points.

--ts-entry-points

Generate entry point typescript per namespace. Implies --gen-all.

--annotate-sparse-vectors

Don’t annotate every vector element.

--annotate SCHEMA

Annotate the provided BINARY_FILE with the specified SCHEMA file.

--no-leak-private-annotation

Prevents multiple types of annotations within a Fbs SCHEMA file. Currently this is required to generate private types in Rust.

--python-no-type-prefix-suffix

Skip emission of Python functions that are prefixed with typenames

--python-typing

Generate Python type annotations

--python-version

Generate code for the given Python version.

--python-gen-numpy

Whether to generate numpy helpers.

--ts-omit-entrypoint

Omit emission of namespace entrypoint file.

--file-names-only

Print out generated file names without writing to the files.

--grpc-filename-suffix SUFFIX

The suffix for the generated file names (Default is .fb).

--grpc-additional-header

Additional headers to prepend to the generated files.

--grpc-use-system-headers

Use <> for headers included from the generated code.

--grpc-search-path PATH

Prefix to any gRPC includes.

--grpc-python-typed-handlers

The handlers will use the generated classes rather than raw bytes.

flatc -c -b schema1.fbs schema2.fbs data.json

Official documentation