bashgogo-echo

How to pass a golang variables( can contain any character) to echo binary in linux?


so my code looks like this , i have a function defined as the following :

func shellOut(command string) (string, string, error) {
    var stdout bytes.Buffer
    var stderr bytes.Buffer
    cmd := exec.Command("bash", "-c", command)
    cmd.Stdout = &stdout
    cmd.Stderr = &stderr
    err := cmd.Run()
    return stdout.String(), stderr.String(), err
}

and a while later i am doing this.

  t := "yoooooooooooo\"oo)(';#oooooooooooo"
    out, stderr, err := shellOut("echo \"" + t + "\"  | ./doOperation.sh")
    if err != nil {
        log.Printf("final error: %v\nstderr: %s", err, stderr)
    }   
    fmt.Println(out)

but i am getting an error that looks like this:

2021/10/14 22:54:18 final error: exit status 1
stderr: bash: -c: line 838: syntax error near unexpected token `('
bash: -c: line 838: `                return "Symbol(" + String(void 0 === t ? "" : t) + ")_" + (++n + r).toString(36)'

and when i give the variable t a value like "yooooo" its gets executed nicely, so how can i pass a variable with any weird character into echo? is there a way to escape all bad character before passing it?


Solution

  • For purely academic purposes, I'm posting this function, as I had to do something similar a while back:

    var bashReplacer = strings.NewReplacer(
        `)`, `\)`, // using back-ticks to keep our sanity
        `(`, `\(`,
        `'`, `\'`,
        `"`, `\"`,
        `$`, `\$`, // include if you don't want variable substitutions
        "`", "\\`", // can't use back-ticks to include a back-tick, so back to double-quotes
    )
    
    func bashEscape(s string) string { return bashReplacer.Replace(s) }
    

    https://play.golang.org/p/uNfI_2MyjcI

    However, as I mentioned in the comments, you can avoid all the pain of shell escaping by just running the target script directly, and feed in your UTF-8 string unaltered like so:

    func execWithStdin(command, stdinText string) (string, string, error) {
        var (
            stdout bytes.Buffer
            stderr bytes.Buffer
        )
    
        cmd := exec.Command(command)
        cmd.Stdin = strings.NewReader(stdinText) // pass in our data via Stdin
        cmd.Stdout = &stdout
        cmd.Stderr = &stderr
        err := cmd.Run()
        return stdout.String(), stderr.String(), err
    }
    

    to use:

    t := `yoooooooooooo"oo)(';#oooooooooooo`
    t += "`" // add a back-tick to make things interesting
    
    // no shell escaping necessary:
    
    out, stderr, err := execWithStdin("./doOperation.sh", t)