Check Unix user

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Check Unix user

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#1 by (0 votes)

2

To verify the user name I can easily use:

import (
    "fmt"
    "os"
)

fmt.Println(os.Getenv("USER"))

But to make things a bit easier I would like to add a new function to struct os , so I did it as follows:

func (system os) Sudo() bool {
    return system.Getenv("USER") == "root"
}

func main() {
    if !os.Sudo() {
        fmt.Println("You have no permission to run as non-root user. Use sudo")
        os.Exit(1)
    }
}

The error I get is:

use of package os without selector

golang

asked by anonymous 19.09.2017 / 15:41

1 answer

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score 0 · Accepted Answer

As far as I know, maybe it's wrong, there's no way to extend functions or interfaces in Golang, created by other packages, much less in this case.

First, you need to set the imports os , but this will not solve the problem.

func (system os) Sudo() bool {
    return system.Getenv("USER") == "root"
}

You actually expect os to be a struct / interface, which in fact it is not. os is a package.

In your case what you can do is create a new folder, for example "systemOS" and then declare "package systemOS", for example:

package systemOS

import "os"

func Sudo() bool {
    return system.Getenv("USER") == "root"
}

Now you could call in your main, as long as you give the import in systemOS newly created:

func main() {
    if !systemOS.Sudo() {
        fmt.Println("You have no permission to run as non-root user. Use sudo")
        os.Exit(1)
    }
}

In other cases, you can create a "synonym" (an alias) for another type. For example, it will be easier to use os/user that contains a struct of user.User .

package main

import (
    "fmt"
    "os/user"
)

type X user.User

func (u X) IsInkeliz() bool {
    return u.Name == "Inkeliz"
}

func main() {
    acc, err := user.Current()
    if err != nil {
        panic("")
    }

    if !X(*acc).IsInkeliz() {
        fmt.Println("Você não é Inkeliz")
    }
}

The X is a type that is the same as user.User . Then I convert X(*acc) and I can access the IsInkeliz() I created, inside the function I also get the .Name that is of the original struct (of the user.User).

Another way to do this would be to create a Struct:

type X struct {
    y *user.User
}

Then put acc inside it and could access y.Name .

However, in all cases you will be creating a new type. I do not know of any way to "extend" the type established by another package without having to create a new type.