ff: github.com/peterbourgon/ff Index | Files | Directories

package ff

import "github.com/peterbourgon/ff"

Package ff is a flags-first helper package for configuring programs.

Runtime configuration must always be specified as commandline flags, so that the configuration surface area of a program is self-describing. Package ff provides an easy way to populate those flags from environment variables and config files.

See the README at https://github.com/peterbourgon/ff for more information.

Index

Package Files

doc.go json.go parse.go

func JSONParser Uses

func JSONParser(r io.Reader, set func(name, value string) error) error

JSONParser is a parser for config files in JSON format. Input should be an object. The object's keys are treated as flag names, and the object's values as flag values. If the value is an array, the flag will be set multiple times.

func Parse Uses

func Parse(fs *flag.FlagSet, args []string, options ...Option) error

Parse the flags in the flag set from the provided (presumably commandline) args. Additional options may be provided to parse from a config file and/or environment variables in that priority order.

func PlainParser Uses

func PlainParser(r io.Reader, set func(name, value string) error) error

PlainParser is a parser for config files in an extremely simple format. Each line is tokenized as a single key/value pair. The first whitespace-delimited token in the line is interpreted as the flag name, and all remaining tokens are interpreted as the value. Any leading hyphens on the flag name are ignored.

type ConfigFileParser Uses

type ConfigFileParser func(r io.Reader, set func(name, value string) error) error

ConfigFileParser interprets the config file represented by the reader and calls the set function for each parsed flag pair.

type Context Uses

type Context struct {
    // contains filtered or unexported fields
}

Context contains private fields used during parsing.

type JSONParseError Uses

type JSONParseError struct {
    Inner error
}

JSONParseError wraps all errors originating from the JSONParser.

func (JSONParseError) Error Uses

func (e JSONParseError) Error() string

Error implenents the error interface.

func (JSONParseError) Unwrap Uses

func (e JSONParseError) Unwrap() error

Unwrap implements the errors.Wrapper interface, allowing errors.Is and errors.As to work with JSONParseErrors.

type Option Uses

type Option func(*Context)

Option controls some aspect of Parse behavior.

func WithAllowMissingConfigFile Uses

func WithAllowMissingConfigFile(allow bool) Option

WithAllowMissingConfigFile tells Parse to permit the case where a config file is specified but doesn't exist. By default, missing config files result in an error.

func WithConfigFile Uses

func WithConfigFile(filename string) Option

WithConfigFile tells Parse to read the provided filename as a config file. Requires WithConfigFileParser, and overrides WithConfigFileFlag. Because config files should generally be user-specifiable, this option should be rarely used. Prefer WithConfigFileFlag.

func WithConfigFileFlag Uses

func WithConfigFileFlag(flagname string) Option

WithConfigFileFlag tells Parse to treat the flag with the given name as a config file. Requires WithConfigFileParser, and is overridden by WithConfigFile.

To specify a default config file, provide it as the default value of the corresponding flag -- and consider also using the WithAllowMissingConfigFile option.

func WithConfigFileParser Uses

func WithConfigFileParser(p ConfigFileParser) Option

WithConfigFileParser tells Parse how to interpret the config file provided via WithConfigFile or WithConfigFileFlag.

func WithEnvVarNoPrefix Uses

func WithEnvVarNoPrefix() Option

WithEnvVarNoPrefix tells Parse to try to set flags from environment variables without any specific prefix. Flag names are matched to environment variables by capitalizing the flag name, and replacing separator characters like periods or hyphens with underscores. By default, flags are not set from environment variables at all.

func WithEnvVarPrefix Uses

func WithEnvVarPrefix(prefix string) Option

WithEnvVarPrefix tells Parse to try to set flags from environment variables with the given prefix. Flag names are matched to environment variables with the given prefix, followed by an underscore, followed by the capitalized flag names, with separator characters like periods or hyphens replaced with underscores. By default, flags are not set from environment variables at all.

func WithEnvVarSplit Uses

func WithEnvVarSplit(delimiter string) Option

WithEnvVarSplit tells Parse to split environment variables on the given delimiter, and to make a call to Set on the corresponding flag with each split token.

func WithIgnoreUndefined Uses

func WithIgnoreUndefined(ignore bool) Option

WithIgnoreUndefined tells Parse to ignore undefined flags that it encounters in config files. By default, if Parse encounters an undefined flag in a config file, it will return an error. Note that this setting does not apply to undefined flags passed as arguments.

type StringConversionError Uses

type StringConversionError struct {
    Value interface{}
}

StringConversionError is returned when a value in a config file can't be converted to a string, to be provided to a flag.

func (StringConversionError) Error Uses

func (e StringConversionError) Error() string

Error implements the error interface.

Directories

PathSynopsis
ffcliPackage ffcli is for building declarative commandline applications.
fftestPackage fftest provides unit test helpers.
fftomlPackage fftoml provides a TOML config file paser.
ffyamlPackage ffyaml provides a YAML config file paser.

Package ff imports 8 packages (graph) and is imported by 17 packages. Updated 2020-04-08. Refresh now. Tools for package owners.