How can I pass a slice as a variadic input?

问题:

I have a function func more(... t). I'm wondering if it's possible to use a slice to populate a list of arguments ... .

I'm trying to solve the following program. Basically to mimic a normal shell which receives the command as a string. Command function requires a "list" of arguments and I don't see how I can convert a string into a such list

    import "os/exec"
    import "strings"
    func main(){
        plainCommand  := "echo hello world"
        sliceA := strings.Fields(plainCommand)
        cmd := exec.Command(sliceA)
    }

回答1:

The Go Programming Language Specification

Passing arguments to ... parameters

If f is variadic with final parameter type ...T, then within the function the argument is equivalent to a parameter of type []T. At each call of f, the argument passed to the final parameter is a new slice of type []T whose successive elements are the actual arguments, which all must be assignable to the type T. The length of the slice is therefore the number of arguments bound to the final parameter and may differ for each call site.

---

Package exec

func Command

func Command(name string, arg ...string) *Cmd

Command returns the Cmd struct to execute the named program with the given arguments.

The returned Cmd's Args field is constructed from the command name followed by the elements of arg, so arg should not include the command name itself. For example, Command("echo", "hello")

---

For example,

package main

import (
    "fmt"
    "os/exec"
)

func main() {
    name := "echo"
    args := []string{"hello", "world"}
    cmd := exec.Command(name, args...)
    out, err := cmd.Output()
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(string(out))
}

Output:

hello world

回答2:

A list of command arguments can be retrieved from the flag package Args() function. You can then pass this to a function using the variadic input style (func(input...))

From the Spec:

If f is variadic with final parameter type ...T, then within the function the argument is equivalent to a parameter of type []T. At each call of f, the argument passed to the final parameter is a new slice of type []T whose successive elements are the actual arguments, which all must be assignable to the type T.

Example:

package main

import "fmt"

func echo(strings ...string) {
    for _, s := range strings {
        fmt.Println(s)
    }
}

func main() {
    strings := []string{"a", "b", "c"}
    echo(strings...) // Treat input to function as variadic
}

See The Go spec for more details.

Playground

回答3:

func Command

func Command(name string, arg ...string) *Cmd

Command returns the Cmd struct to execute the named program with the given arguments.

So you have to extract the command which is found at sliceA[0] and then pass all the arguments with a variadic but removing the command sliceA[1:]....

import "os/exec"
import "strings"
func main(){
    plainCommand  := "echo hello world"
    sliceA := strings.Fields(plainCommand)
    cmd := exec.Command(sliceA[0], sliceA[1:]...)
}