Command line argument parser following the GNU standard.
./test -vo out.png --size 256 input.txt
with the following features:
- build-in help (
-hand--help) message - scan arguments into struct fields with configuration in tags
- scan into composite field types (arrays, slices, structs)
- allow for nested sub commands
GNU command line argument rules:
- arguments are options when they begin with a hyphen
- - multiple options can be combined:
-abcis the same as-a -b -c - long options start with two hyphens:
--abcis one option - option names are alphanumeric characters
- options can have a value:
-a 1means thatahas value1 - option values can be separated by a space, equal sign, or nothing:
-a1 -a=1 -a 1are all equal - options and non-options can be interleaved
- options may appear in any order
- the argument
--terminates all options so that all following arguments are treated as non-options - an argument value of
-is allowed, usually used to mean standard in or out streams - options may be specified multiple times, only the last one determines its value
Additional features:
- counting options:
-vvvsetsv = 3 - appending options:
-v 1 -v 2setsv = []int{1, 2} - boolean options:
--varenables and--no-vardisables a boolean - options can be composite types, such as structs, slices, or maps:
-v 1,2,3setsv = []int{1, 2, 3}-v [1 2 3]setsv = []int{1, 2, 3}-v {1:one 2:two}setsmap[int]string{1:"one", 2:"two"}-v {string 42 [0 1]}setsstruct{S string, I int, B [2]bool}{"string", 42, false, true}
- options can retrieve their list/dict values from a source (such as SQL):
-v file:email-addresses.txtsetsv = []string{ /* lines in email-addresses.txt */ }-v file:email-addresses.txtsetsv = map[string]string{ /* key=value in email-addresses.txt lines */ }
See also github.com/tdewolff/prompt for a command line prompter.
Make sure you have Git and Go (1.22 or higher) installed, run
mkdir Project
cd Project
go mod init
go get -u github.com/tdewolff/argp
Then add the following import
import (
"github.com/tdewolff/argp"
)A regular command with short and long options.
See cmd/test/main.go.
package main
import "github.com/tdewolff/argp"
func main() {
var verbose int
var input string
var output string
var files []string
size := 512 // default value
cmd := argp.New("CLI tool description")
cmd.AddOpt(argp.Count{&verbose}, "v", "verbose", "Increase verbosity, eg. -vvv")
cmd.AddOpt(&output, "o", "output", "Output file name")
cmd.AddOpt(&size, "", "size", "Image size")
cmd.AddArg(&input, "input", "Input file name")
cmd.AddRest(&files, "files", "Additional files")
cmd.Parse()
// ...
}with help output
Usage: test [options] input files...
Options:
-h, --help Help
-o, --output string Output file name
--size=512 int Image size
-v, --verbose int Increase verbosity, eg. -vvv
Arguments:
input Input file name
files Additional files
Example with sub commands using a main command for when no sub command is used, and a sub command named "cmd". For the main command we can also use New and AddOpt instead and process the command after argp.Parse().
package main
import "github.com/tdewolff/argp"
func main() {
cmd := argp.NewCmd(&Main{}, "CLI tool description")
cmd.AddCmd(&Command{}, "cmd", "Sub command")
cmd.Parse()
}
type Main struct {
Version bool `short:"v"`
}
func (cmd *Main) Run() error {
// ...
}
type Command struct {
Verbose bool `short:"v" name:""`
Output string `short:"o" desc:"Output file name"`
Size int `default:"512" desc:"Image size"`
}
func (cmd *Command) Run() error {
// ...
}var input string
cmd.AddArg(&input, "input", "Input file name")
var files []string
cmd.AddRest(&files, "files", "Additional input files")Basic types
var v string = "default"
cmd.AddOpt(&v, "v", "var", "description")
var v bool = true
cmd.AddOpt(&v, "v", "var", "description")
var v int = 42 // also: int8, int16, int32, int64
cmd.AddOpt(&v, "v", "var", "description")
var v uint = 42 // also: uint8, uint16, uint32, uint64
cmd.AddOpt(&v, "v", "var", "description")
var v float64 = 4.2 // also: float32
cmd.AddOpt(&v, "v", "var", "description")Composite types
v := [2]int{4, 2} // element can be any valid basic or composite type
cmd.AddOpt(&v, "v", "var", "description")
// --var [4 2] => [2]int{4, 2}
// or: --var 4,2 => [2]int{4, 2}
v := []int{4, 2, 1} // element can be any valid basic or composite type
cmd.AddOpt(&v, "v", "var", "description")
// --var [4 2 1] => []int{4, 2, 1}
// or: --var 4,2,1 => []int{4, 2, 1}
v := map[int]string{1:"one", 2:"two"} // key and value can be any valid basic or composite type
cmd.AddOpt(&v, "v", "var", "description")
// --var {1:one 2:two} => map[int]string{1:"one", 2:"two"}
v := struct { // fields can be any valid basic or composite type
S string
I int
B [2]bool
}{"string", 42, [2]bool{0, 1}}
cmd.AddOpt(&v, "v", "var", "description")
// --var {string 42 [0 1]} => struct{S string, I int, B [2]bool}{"string", 42, false, true}Count the number of time a flag has been passed.
var c int
cmd.AddOpt(argp.Count{&c}, "c", "count", "Count")
// Count the number of times flag is present
// -c -c / -cc / --count --count => 2
// or: -c 5 => 5Append each flag to a list.
var v []int
cmd.AddOpt(argp.Append{&v}, "v", "value", "Values")
// Append values for each flag
// -v 1 -v 2 => [1 2]Load all arguments from a configuration file. Currently only TOML is supported.
cmd.AddOpt(&argp.Config{cmd, "config.toml"}, "", "config", "Configuration file")Use a list source specified as type:list. Default supported types are: inline.
- Inline takes a []string, e.g.
inline:[foo bar]
list := argp.NewList(il)
defer list.Close()
cmd.AddOpt(&list, "", "list", "List")You can add a MySQL source:
type mysqlList struct {
Hosts string
User string
Password string
Dbname string
Query string
}
func newMySQLList(s []string) (argp.ListSource, error) {
if len(s) != 1 {
return nil, fmt.Errorf("invalid path")
}
t := mysqlList{}
if err := argp.LoadConfigFile(&t, s[0]); err != nil {
return nil, err
}
uri := fmt.Sprintf("%s:%s@%s/%s", t.User, t.Password, t.Hosts, t.Dbname)
db, err := sqlx.Open("mysql", uri)
if err != nil {
return nil, err
}
db.SetConnMaxLifetime(time.Minute)
db.SetConnMaxIdleTime(time.Minute)
db.SetMaxOpenConns(10)
db.SetMaxIdleConns(10)
return argp.NewSQLList(db, t.Query, "")
}
// ...
list.AddSource("mysql", newMySQLList)
// ...
Use as ./bin -list mysql:list-config.toml.
Use a dict source specified as type:dict. Default supported types are: static and inline.
- Static takes a string and will return that as a value for all keys, e.g.
static:foobar - Inline takes a map[string]string, e.g.
inline:{foo:1 bar:2}
dict := argp.NewDict([]string{"static:value"})
defer dict.Close()
cmd.AddOpt(&dict, "", "dict", "Dict")You can add custom sources must like the mysqlList example above.
The following struct will accept the following options and arguments:
-vor--varwith a default value of 42- The first argument called
firstwith a default value of 4.2 - The other arguments called
rest
type Command struct {
Var1 int `short:"v" name:"var" default:"42" desc:"Description"`
Var2 float64 `name:"first" index:"0" default:"4.2"`
Var3 []string `name:"rest" index:"*"`
}
func (cmd *Command) Run() error {
// run command
return nil
}Released under the MIT license.