An extendable argument parser for Golang. Mostly follows the GNU Program Argument Syntax Conventions.

Use go get maunium.net/go/mauflag to get this package

A flag can have as many long or short keys as you like. Short keys are prefixed with one dash (-) whilst long keys are prefixed with two (--)

To create a flag, you must first call the Make() method in a flagset. Calling flagset methods as package functions uses the default flagset which takes input arguments from os.Args

After creating a flag, you can call the functions it has as you like. After configuring the flag, you can call one of the type functions to set the flag type and get a pointer to the value.

Here's a basic string flag that can be set using -s or --my-string-flag

var myStringFlag = flag.Make().ShortKey("s").LongKey("my-string-flag").Default("a string").String()

The following input arguments would set the value of the flag to foo

• -s, foo
• -s=foo
• -sfoo
• --my-string-flag, foo
• --my-string-flag=foo

Short boolean flags can be chained. The last flag of a chain doesn't necessarily have to be a boolean flag. For example, if we had the following flags defined

var boolA = flag.Make().ShortKey("a").Bool()
var boolB = flag.Make().ShortKey("b").Bool()
var boolC = flag.Make().ShortKey("c").Bool()
var stringD = flag.Make().ShortKey("d").String()

We could set the values of all the boolean flags to true with one input argument: -abc. We could also add the d flag to the end like so: -abcd, foo. Any of the other ways to set short flags also work (-abcd=foo, -abcdfoo).

However, if you put d as the first flag (-dabc) the value of the d flag will be abc and none of the boolean flags would change.

More docs, including all values supported by default, can be found from godoc.org/maunium.net/go/mauflag

All value containers must implement the Value interface. It contains two functions:

• Set(string) which is called whenever the parser finds a value associated with the flag.
• Name() which should return a human-readable name for the type of the value. If the value container contains multiple actual values, Name() should return the name of a single object (e.g. integer if the value container contains multiple integers)

After creating a value container you can use it by calling the Custom method of a Flag and giving an instance of the value container. The parser will then call the Set method each time it encounters a value associated with the flag.