Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

https://github.com/akamensky/argparse

Argparse for golang. Just because `flag` sucks
https://github.com/akamensky/argparse

argparse argument-parser awesome-go cli cli-app command-line-parser go golang

Last synced: about 1 month ago
JSON representation

Argparse for golang. Just because `flag` sucks

Lists

README 

        
# Golang argparse



[![](https://img.shields.io/static/v1?label=Sponsor&message=%E2%9D%A4&logo=GitHub&color=%23fe8e86)](https://github.com/sponsors/akamensky) [![Go Reference](https://pkg.go.dev/badge/github.com/akamensky/argparse.svg)](https://pkg.go.dev/github.com/akamensky/argparse) [![Go Report Card](https://goreportcard.com/badge/github.com/akamensky/argparse)](https://goreportcard.com/report/github.com/akamensky/argparse) [![Coverage Status](https://coveralls.io/repos/github/akamensky/argparse/badge.svg?branch=master)](https://coveralls.io/github/akamensky/argparse?branch=master) [![Build Status](https://travis-ci.org/akamensky/argparse.svg?branch=master)](https://travis-ci.org/akamensky/argparse)



Let's be honest -- Go's standard command line arguments parser `flag` terribly sucks. 

It cannot come anywhere close to the Python's `argparse` module. This is why this project exists.



The goal of this project is to bring ease of use and flexibility of `argparse` to Go. 

Which is where the name of this package comes from.



#### Installation



To install and start using argparse simply do:



```

$ go get -u -v github.com/akamensky/argparse

```



You are good to go to write your first command line tool!

See Usage and Examples sections for information how you can use it



#### Usage



To start using argparse in Go see above instructions on how to install.

From here on you can start writing your first program.

Please check out examples from `examples/` directory to see how to use it in various ways.



Here is basic example of print command (from `examples/print/` directory):

```go

package main



import (

	"fmt"

	"github.com/akamensky/argparse"

	"os"

)



func main() {

	// Create new parser object

	parser := argparse.NewParser("print", "Prints provided string to stdout")

	// Create string flag

	s := parser.String("s", "string", &argparse.Options{Required: true, Help: "String to print"})

	// Parse input

	err := parser.Parse(os.Args)

	if err != nil {

		// In case of error print error and print usage

		// This can also be done by passing -h or --help flags

		fmt.Print(parser.Usage(err))

	}

	// Finally print the collected string

	fmt.Println(*s)

}

```



#### Basic options



Create your parser instance and pass it program name and program description.

Program name if empty will be taken from `os.Args[0]` (which is okay in most cases).

Description can be as long as you wish and will be used in `--help` output

```go

parser := argparse.NewParser("progname", "Description of my awesome program. It can be as long as I wish it to be")

```



String will allow you to get a string from arguments, such as `$ progname --string "String content"`

```go

var myString *string = parser.String("s", "string", ...)

```



Positional arguments can be used like this `$ progname value1`.

See [Basic Option Structure](#basic-option-structure) and [Positionals](#positionals).

```go

var myString *string = parser.StringPositional(nil)

var myString *string = parser.FilePositional(nil)

var myString *string = parser.FloatPositional(nil)

var myString *string = parser.IntPositional(nil)

var myString *string = parser.SelectorPositional([]string{"a", "b"}, nil)

var myString1 *string = parser.StringPositional(Options{Default: "beep"})

```



Selector works same as a string, except that it will only allow specific values.

For example like this `$ progname --debug-level WARN`

```go

var mySelector *string = parser.Selector("d", "debug-level", []string{"INFO", "DEBUG", "WARN"}, ...)

```



StringList allows to collect multiple string values into the slice of strings by repeating same flag multiple times.

Such as `$ progname --string hostname1 --string hostname2 -s hostname3`

```go

var myStringList *[]string = parser.StringList("s", "string", ...)

```



List allows to collect multiple values into the slice of strings by repeating same flag multiple times 

(at fact - it is an Alias of StringList).

Such as `$ progname --host hostname1 --host hostname2 -H hostname3`

```go

var myList *[]string = parser.List("H", "hostname", ...)

```



Flag will tell you if a simple flag was set on command line (true is set, false is not).

For example `$ progname --force`

```go

var myFlag *bool = parser.Flag("f", "force", ...)

```



FlagCounter will tell you the number of times that  simple flag  was set on command line 

(integer greater than or equal to 1 or 0 if not set).

For example `$ progname -vv --verbose`

```go

var myFlagCounter *int = parser.FlagCounter("v", "verbose", ...)

```



Int will allow you to get a decimal integer from arguments, such as `$ progname --integer "42"`

```go

var myInteger *int = parser.Int("i", "integer", ...)

```



IntList allows to collect multiple decimal integer values into the slice of integers by repeating same flag multiple times.

Such as `$ progname --integer 42 --integer +51 -i -1`

```go

var myIntegerList *[]int = parser.IntList("i", "integer", ...)

```



Float will allow you to get a floating point number from arguments, such as `$ progname --float "37.2"`

```go

var myFloat *float64 = parser.Float("f", "float", ...)

```



FloatList allows to collect multiple floating point number values into the slice of floats by repeating same flag multiple times.

Such as `$ progname --float 42 --float +37.2 -f -1.0`

```go

var myFloatList *[]float64 = parser.FloatList("f", "float", ...)

```



File will validate that file exists and will attempt to open it with provided privileges.

To be used like this `$ progname --log-file /path/to/file.log`

```go

var myLogFile *os.File = parser.File("l", "log-file", os.O_RDWR, 0600, ...)

```



FileList allows to collect files into the slice of files by repeating same flag multiple times.

FileList will validate that files exists and will attempt to open them with provided privileges.

To be used like this `$ progname --log-file /path/to/file.log --log-file /path/to/file_cpy.log -l /another/path/to/file.log`

```go

var myLogFiles *[]os.File = parser.FileList("l", "log-file", os.O_RDWR, 0600, ...)

```



You can implement sub-commands in your CLI using `parser.NewCommand()` or go even deeper with `command.NewCommand()`.

Addition of a sub-command implies that a subcommand is required.

Sub-commands are always parsed before arguments.

If a command has `Positional` arguments and sub-commands then sub-commands take precedence.

Since parser inherits from command, every command supports exactly same options as parser itself,

thus allowing to add arguments specific to that command or more global arguments added on parser itself!



You can also dynamically retrieve argument values and if they were parsed:

```

var myInteger *int = parser.Int("i", "integer", ...)

parser.Parse()

fmt.Printf("%d", *parser.GetArgs()[0].GetResult().(*int))

fmt.Printf("%v", *parser.GetArgs()[0].GetParsed())

```



#### Basic Option Structure



The `Option` structure is declared at `argparse.go`:

```go

type Options struct {

	Required bool

	Validate func(args []string) error

	Help     string

	Default  interface{}

}

```



You can set `Required` to let it know if it should ask for arguments.

Or you can set `Validate` as a lambda function to make it know while value is valid.

Or you can set `Help` for your beautiful help document.

Or you can set `Default` will set the default value if user does not provide a value.



Example:

```

dirpath := parser.String("d", "dirpath",

			 &argparse.Options{

			 	Required: false,

				Help: "the input files' folder path",

				Default: "input",

			})

```



#### Caveats



There are a few caveats (or more like design choices) to know about:

* Shorthand arguments MUST be a single character. Shorthand arguments are prepended with single dash `"-"`

* If not convenient shorthand argument can be completely skipped by passing empty string `""` as first argument

* Shorthand arguments ONLY for `parser.Flag()` and  `parser.FlagCounter()` can be combined into single argument same as `ps -aux`, `rm -rf` or `lspci -vvk` 

* Long arguments must be specified and cannot be empty. They are prepended with double dash `"--"`

* You cannot define two same arguments. Only first one will be used. For example doing `parser.Flag("t", "test", nil)` followed by `parser.String("t", "test2", nil)` will not work as second `String` argument will be ignored (note that both have `"t"` as shorthand argument). However since it is case-sensitive library, you can work arounf it by capitalizing one of the arguments

* There is a pre-defined argument for `-h|--help`, so from above attempting to define any argument using `h` as shorthand will fail

* `parser.Parse()` returns error in case of something going wrong, but it is not expected to cover ALL cases

* Any arguments that left un-parsed will be regarded as error



##### Positionals

* `Positional` args have a set of effects and conditions:

  * Always parsed after subcommands and non-positional args

  * Always set Required=False

  * Default is only used if the command or subcommand owning the arg `Happened`

  * Parsed in Command root->leaf left->right order (breadth-first)

	* Top level cmd consumes as many positionals as it can, from left to right

	* Then in a descendeding loop for any command which `Happened` it repeats

	* Positionals which are not satisfied (due to lack of input args) are not errors



#### Contributing



Can you write in Go? Then this projects needs your help!



Take a look at open issues, specially the ones tagged as `help-wanted`.

If you have any improvements to offer, please open an issue first to ensure this improvement is discussed.



There are following tasks to be done:

* Add more examples

* Improve code quality (it is messy right now and could use a major revamp to improve gocyclo report)

* Add more argument options (such as numbers parsing)

* Improve test coverage

* Write a wiki for this project



However note that the logic outlined in method comments must be preserved 

as the the library must stick with backward compatibility promise!



#### Acknowledgments



Thanks to Python developers for making a great `argparse` which inspired this package to match for greatness of Go