docker run -w从go脚本运行时出现意外错误

Question

I'm writing a very simple script that just formats a build command via docker for go apps. It formats the command like this:

docker run --rm -v c:/Users/me/go/src/goapp:/go/src/goapp -w /go/src/goapp -e GOOS=os -e GOARCH=arch image go build -v -o outputname

When running this, however I get the following:

docker: Error response from daemon: the working directory ' /go/src/goapp' is invalid, it needs to be an absolute path

I tried reformatting it like this:

docker run --rm -v="c:/Users/me/go/src/goapp:/go/src/goapp" -w="/go/src/goapp" -e="GOOS=os" -e"GOARCH=arch" image go build -v -o outputname

and get the same error, only the "invalid" working directory is "/go/src/goapp"

Here's my code:

package main

import (
    "bytes"
    "flag"
    "fmt"
    "os"
    "os/exec"
    "runtime"
    "strings"
)

func constructCmd(volumeMap, workingDir, goos, goarch, output, image string) []string {
    finalCmd := append([]string{"run", "--rm"},
        fmt.Sprintf("-v='%s'", volumeMap),
        fmt.Sprintf("-w='%s'", workingDir),
        fmt.Sprintf("-e='%s'", goos),
        fmt.Sprintf("-e='%s'", goarch),
    )

    finalCmd = append(finalCmd, image, "go build -v")

    if output != "" {
        finalCmd = append(finalCmd, fmt.Sprintf("-o %s", output))
    }

    return finalCmd
}

func main() {
    // Parse flags
    osPtr := flag.String("os", "windows", "Target distribution")
    archPtr := flag.String("arch", "amd64", "Target distribution")
    outputPtr := flag.String("out", "", "Output file name")
    flag.Parse()

    fmt.Printf("Building for %s/%s:
", *osPtr, *archPtr)

    goos := "GOOS=" + *osPtr
    goarch := "GOARCH=" + *archPtr

    pwd, _ := os.Getwd()
    if runtime.GOOS == "windows" {
        pwd = strings.Replace(pwd, "C", "c", 1)
        pwd = strings.Replace(pwd, "\\", "/", -1)
    }
    workingDir := pwd[strings.Index(pwd, "/go"):]
    volumeMap := fmt.Sprintf("%s:%s", pwd, workingDir)

    var image string
    if len(flag.Args()) == 0 {
        image = "golang"
    } else {
        image = flag.Args()[0]
    }

    execCmd := constructCmd(volumeMap, workingDir, goos, goarch, *outputPtr, image)

    cmd := exec.Command("docker", execCmd...)
    cmdOutput := &bytes.Buffer{}
    cmd.Stdout = cmdOutput
    cmd.Stderr = cmdOutput
    err := cmd.Run()
    if err != nil {
        os.Stderr.WriteString(err.Error())
    }
    fmt.Print(string(cmdOutput.Bytes()))
}

To note, if I run this command directly, it works no problem. No error. So this isn't a docker problem, it's a go problem. What could cause this error?

Answer 1

Remove the quoted quotes. As stated in the exec package's documentation, Go's standard lib os/exec package does not invoke the shell to execute a Cmd:

Unlike the "system" library call from C and other languages, the os/exec package intentionally does not invoke the system shell and does not expand any glob patterns or handle other expansions, pipelines, or redirections typically done by shells. The package behaves more like C's "exec" family of functions.

Unless you're calling the shell in your command, there's no shell being invoked to process and remove those quotes.

For example, this:

"-v='%s'"

Should be this:

"-v=%s"

---

Update from comments: OP also found and fixed a second issue:

"go build -v"

needed to be split up into separate arguments:

"go", "build", "-v"