goptions

Overview ¶

package goptions implements a flexible parser for command line options.

Key targets were the support for both long and short flag versions, mutually exclusive flags, and verbs. Flags and their corresponding variables are defined by the tags in a (possibly anonymous) struct.

var options struct {
	Name string `goptions:"-n, --name"`
	Force bool `goptions:"-f, --force"`
	Verbosity int `goptions:"-v, --verbose"`
}

Short flags can be combined (e.g. `-nfv`). Long flags take their value after a separating space. The equals notation (`--long-flag=value`) is NOT supported right now.

Every member of the struct which is supposed to catch a command line value has to have a "goptions" tag. The contains the short and long flag names for this member but can additionally specify any of these options below.

obligatory        - Flag must be specified. Otherwise an error will be returned
                    when Parse() is called.
description='...' - Set the description for this particular flag. Will be
                    used by the HelpFunc.
mutexgroup='...'  - Add this flag to a MutexGroup. Only one flag of the
                    ones sharing a MutexGroup can be set. Otherwise an error
                    will be returned when Parse() is called. If one flag in a
                    MutexGroup is `obligatory` one flag of the group must be
                    specified. A flag can be in multiple MutexGroups at once.

Depending on the type of the struct member, additional options might become available:

Type: *os.File
    The given string is interpreted as a path to a file. If the string is "-"
    os.Stdin or os.Stdout will be used. os.Stdin will be returned, if the
    `rdonly` flag was set. os.Stdout will be returned, if `wronly` was set.
Available options:
    Any combination of create, append, rdonly, wronly, rdwr,
    excl, sync, trunc and perm can be specified and correspond directly with
    the combination of the homonymous flags in the os package.

Type: *net.TCPAddr
    The given string is interpreted as a tcp address. It is passed to
    net.ResolvTCPAddr() with "tcp" as the network type identifier.

Type: *net/url.URL
    The given string is parsed by net/url.Parse()

Type: time.Duration
    The given string is parsed by time.ParseDuration()

If a member is a slice type, multiple definitions of the flags are possible. For each specification the underlying type will be used.

var options struct {
    Servers []string `goptions:"-s, --server, description='Servers to connect to'"`
}{}

goptions also has support for verbs. Each verb accepts its own set of flags which take exactly the same tag format as global options. For an usage example of verbs see the PrintHelp() example.