How Can I Execute External Commands as a Different User in Go?

Executing External Commands Under a Different User with Go

In the vast landscape of system programming, the ability to execute external commands under the auspices of a different user is often indispensable. While traditional methods may involve leveraging the "su" or "bash" utilities, a more efficient and pure Go-based approach can be achieved.

To accomplish this task, the os/exec package provides a comprehensive set of functions for managing external process execution. However, its default behavior runs commands under the privileges of the current process. To execute commands as a different user, we delve into the realm of the syscall.Credential struct.

By adding a Credential structure to the SysProcAttr field of the Cmd object, we can specify the credentials (i.e., UID and GID) under which the external command should execute. The following code snippet demonstrates this approach:

package main

import (
    "fmt"
    "os/exec"
    "strconv"
    "syscall"
)

func main() {
    // Capture the UID of the desired user
    u, err := user.Lookup("another_user")
    if err != nil {
        fmt.Printf("%v", err)
        return
    }

    // Parse the UID into an integer and construct the Credential
    uid, err := strconv.Atoi(u.Uid)
    if err != nil {
        fmt.Printf("%v", err)
        return
    }
    credential := &syscall.Credential{Uid: uid}

    // Compose the command
    command := exec.Command("ls", "-l")

    // Configure the command's SysProcAttr with the Credential
    command.SysProcAttr = &syscall.SysProcAttr{}
    command.SysProcAttr.Credential = credential

    // Execute the command and process its output
    output, err := command.CombinedOutput()
    if err != nil {
        fmt.Printf("%v", err)
        return
    }

    fmt.Println(string(output))
}

With this approach, we gain fine-grained control over the execution environment of our external commands, empowering us to precisely specify the user under which they should execute.

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