os/exec: Cannot execute command with space in the name on Windows, when there are parameters

[calmh]

Go 1.7.1 on windows-amd64, Windows 10 latest.

Consider a test project:

src/github.com/calmh/wincmdtest/
    main.go
    folder name/
        test.bat

main.go contents:

package main

import (
    "fmt"
    "os/exec"
    "strings"
)

func main() {
    execCmd("./folder name/test.bat")
    execCmd("./folder name/test.bat", "one param")
}

func execCmd(path string, args ...string) {
    fmt.Printf("Running: %q %q\n", path, strings.Join(args, " "))
    cmd := exec.Command(path, args...)
    bs, err := cmd.CombinedOutput()
    fmt.Printf("Output: %s", bs)
    fmt.Printf("Error: %v\n\n", err)
}

folder name/test.bat contents:

@echo off
echo Success

Expected output is two runs with "Success" in them.

Actual:

C:\Users\jb\Go\src\github.com\calmh\wincmdtest>go run main.go
Running: "./folder name/test.bat" ""
Output: Success
Error: <nil>

Running: "./folder name/test.bat" "one param"
Output: '.' is not recognized as an internal or external command,
operable program or batch file.
Error: exit status 1

It appears that having params on a command, where the command contains a space, breaks the parsing of it. I haven't been able to work around this by experimenting with various ways of quoting the command, using backslashes or slashes, etc.

[calmh]

I started following this down through syscall.StartProcess, but not really being a Windows programmer I ran into unacceptable levels of nope almost immediately so probably won't try to fix this myself, sorry. :(

[alexbrainman]

It appears that having params on a command, where the command contains a space, breaks the parsing of it.

Go encodes child process parameters in a way that is understood by most programs. Go uses rules similar to what CommandLineToArgvW implements.

Unfortunately, your child process is cmd.exe (cmd.exe is called to execute the batch file you've requested). And cmd.exe parses its input parameters differently.

You can read this very long post http://daviddeley.com/autohotkey/parameters/parameters.htm#WIN about it all.

I haven't been able to work around this by experimenting with various ways of quoting the command, using backslashes or slashes, etc.

You should stop using exec.Command to build your child process command line, and build it yourself (as per rules described in the doco I mentioned). Then you can pass raw command line to your child process by setting exec.Cmd.SysProcAttr to syscall.SysProcAttr with CmdLine set appropriately.

Maybe we could fix this problem by changing Go encoding algorithm to use cmd.exe rules every time we execute batch file.

There is more of the same discussion on issue #15566.

Alex

[mattn]

I guess this should be fixed by small change.

diff --git a/src/syscall/exec_windows.go b/src/syscall/exec_windows.go
index cafce1e..a0e1f56 100644
--- a/src/syscall/exec_windows.go
+++ b/src/syscall/exec_windows.go
@@ -91,6 +91,9 @@ func makeCmdLine(args []string) string {
        }
        s += EscapeArg(v)
    }
+   if s != "" && s[0] == '"' && len(args) > 1 {
+       s = `"` + s + `"`
+   }
    return s
 }

If the first argument contain spaces, and it have arguments (no matter if the argument not contains spaces), whole of string should be quoted.

c:\dev\go-sandbox\space>go run main.go
Running: ".\\folder name\\test.bat" ""
Output: Success
Error: <nil>

Running: ".\\folder name\\test.bat" "one param"
Output: Success
Error: <nil>

[gopherbot]

CL https://golang.org/cl/32490 mentions this issue.

[rsc]

Postponing decisions about this to Go 1.9.