在go中使用curl和命令

Question

I'm using Go with command to execute curl which works as expected

curl := exec.Command("curl", "https://services.odata.org/V3/northwind/northwind.svc/")
    out, err := curl.Output()
    if err != nil {
        fmt.Println("erorr" , err)
        return
    }
    fmt.Println(out)

Now I want to use some placeholders like

curl -O http://quiet-waters-1228.herokuapp.com/assets/image.jpg

but now I need to get the url for command e.g. if I run in bash mytool url I got the url value

`curl -O $(mytool url)`

The problem is that we need to execute the command in the code and I'm not sure how to pass it

curl := exec.Command("curl", "curl -O $(url)")
        out, err := curl.Output()
        if err != nil {
            fmt.Println("erorr" , err)
            return
        }
        fmt.Println(out)

Answer 1

In os package you have slice of strings which contains all arguments passed by shell to your program.

os.Args 0th value, i.e., first element is going to be name of the command itself.

If your tool command is mytool, os.Args[0] contains mytool.

Rest are going to be the arguments, which are passed by shell.

package main

import (
    "log"
    "os"
    "os/exec"
)

func main() {

    if len(os.Args) < 2 {
        // If argument is not provided quit
        log.Fatalln("url not provided")
    }
    url := os.Args[1] // URL

    cmd := exec.Command("curl", "-O", url)
    cmd.Run()
}

You can also download multiple URLs concurrently,

var wg *sync.WaitGroup

func main() {
    urls := os.Args[1:]

    wg = new(sync.WaitGroup)
    wg.Add(len(urls))

    for _, url := range urls {
        go download(url)
    }

    wg.Wait()
}

func download(url string) {
    defer wg.Done()
    cmd := exec.Command("curl", "-O", url)
    cmd.Run()
}