gyb

Estimate the number and the size of all emails on your Gmail account

$ gyb --email [email@gmail.com] --action estimate

$ gyb --email [email@gmail.com] --action backup --local-folder [path/to/directory]

$ gyb --email [email@gmail.com] --search "[is:important OR is:starred]"

$ gyb --email [email@gmail.com] --action restore --local-folder [path/to/directory]

gyb [options...] [input.gyb [output]]

-h, --help
    Display usage summary and exit

--line-directive PREFIX
    Emit #line directives with given prefix (default: empty string)

--define KEY=VALUE
    Define global template variable (repeatable)

--lambda NAME=FILE
    Load Python lambda function from file (repeatable)

--indexing-depth N
    Max recursion depth for indexing (default: 20)

gyb (Generate Your Boilerplate) is a powerful command-line tool for generating code from text templates using embedded Python logic. Developed primarily for Apple's Swift project, it processes input files with special directives like %if, %elif, %else, %for, %end, and Python expressions delimited by %{ %}.

Indentation is preserved intelligently, making it ideal for languages like Swift, C++, or any structured format. Variables can be defined via command-line options, lambdas loaded from files, and #line directives emitted for source mapping during debugging.

Common workflow: gyb template.gyb --define Name=SwiftString > SwiftString.swift. It supports stdin/stdout for piping and generates output directly or to a file. Python exceptions in templates cause immediate failure with stack traces, aiding development. Widely used in LLVM, Clang, and Swift standard library for repetitive code like operator overloads or enum definitions.

Requires Python 3.x; whitespace/indentation-sensitive; template Python errors halt with traceback; no built-in caching.

%if condition, %for var in iterable, %end; expressions: %{ py_expr %}; comments: %%.

gyb --line-directive '' --define Lang=Swift Enum.gyb -o Enum.swift
Template snippet: %for case in cases: % case %{case.name}%: ...

Created ~2015 for Apple's Swift toolchain (utils/gyb.py); evolved for LLVM/Swift stdlib codegen; open-sourced under Apache 2.0.

m4(1), cpp(1)