flagParse

FlagParse is a software component used to interpret command-line flags and options supplied to a program. It standardizes the extraction of user-provided switches such as --verbose or -v into structured values that the program can use at runtime. FlagParse is usually provided as a library or module and is a core part of many console applications.

Common features include support for long and short flags, values of different types (boolean, string, integer, etc.), default values, required flags, and automatic generation of usage information. Many implementations also support repeated flags, list or array values, and the ability to read flag values from environment variables or configuration files. Robust error handling reports unknown or malformed flags and can present a help screen.

Architecturally, a flagParse system maintains a registry of defined flags, each with a name, optional shorthand, type, default value, and help text. A parser reads the command-line arguments, matches flags, converts their values to the declared types, and stores the results. The resulting values are exposed to the program through variables or accessors, and a separate usage or help generator can render guidance for users.

Usage typically involves defining the flagged options before parsing, invoking a parse routine with the program arguments, and then using the resulting values to drive program behavior. This pattern helps separate argument handling from business logic and makes tests easier.

FlagParse concepts exist across programming languages. In many ecosystems, similar functionality is provided under different names by libraries or standard packages, such as the Go flag package, Python's argparse, or Node.js libraries like yargs. FlagParse emphasizes consistent parsing, error reporting, and user-friendly help output.

See also: command-line interface, option parsing, getopt, argparse, flag package, yargs.