flagstruct 🏁

flagstruct is another library for parsing command line flags into structs. Although packages named flagstruct already exist, this pattern emerged coincidentally in some of our projects, and we decided to simply merge the best parts into one library. We noticed the name was already taken too late. "Any resemblance to actual persons, living or dead, or actual events is purely coincidental."

flagstruct has a few neat advantages:

• Uses values as defaults; no need to encode these as struct tags.
• Supports generating usage data with groups and specified ordering. To use grouping, simply use an unnamed struct{}-typed member as a separator.
• Supports custom flag.Value types in structures, along with the built-in flag.Value types.
• Implements FlagSets akin to Go's flag.FlagSet.
• Implements environment variables through env flag.
• Boolean special case is handled identically to Go's flag package.

Getting Started

flagstruct is a library. To make use of it, you need to write software that imports it. An example is included below that you can use to play around with flagstruct.

Prerequisites

flagstruct is built in the Go programming language. If you are new to Go, you will need to install Go.

There are no other dependencies, but you may want to configure your text editor for Go if you have not done so.

Acquiring

Next, you'll want to go get flagstruct, like so:

go get github.com/Benzinga/flagstruct

If your $GOPATH is configured, and git is setup to know your credentials, in a few moments the command should complete with no output. The repository will exist under $GOPATH/src/github.com/Benzinga/flagstruct. It cannot be moved from this location.

Hint: If you've never used Go before, your $GOPATH will be under the go folder of your user directory.

Example

A quick example follows:

package main

import (
    "flag"
    "fmt"

    "github.com/Benzinga/flagstruct"
)

var conf = struct {
    Compress bool   `flag:"z" usage:"whether or not to use compression" env:"COMPRESS"`
    OutputFn string `flag:"out" usage:"output ~filename~"`
}{
    Compress: true,
}

func main() {
    // Parse flags and environment based off of flagstruct.
    flagstruct.Configure(&conf)

    // Print out the flags.
    fmt.Printf("Flags: %+v\n", conf)
}

To use this example: Save to a file with a .go extension, like test.go, then use go run test.go [args] to play with the argument parsing. Do not put the example file into the flagstruct directory as it will get confused with the flagstruct source code.