How to set default permission mask in Golang

In Linux systems, Umask refers to the default permission mask when a file is created. When we create a new file, the system determines the actual permissions of the file based on the default permission mask. If we do not set a default permission mask, the system will use 022 as the default permission mask by default, which means that the created file permissions are 644. But sometimes we need to set different permission masks to meet different needs. This article will introduce how to set the default permission mask in Golang.

First of all, we need to understand how to set umask in Linux system. Normally, we can set the default umask value in the system startup file (such as /etc/profile, /etc/login.defs, etc.). For example, if we want to set the umask to 002, we can add the following line to the startup file:

umask 002

After setting the umask value, the permissions of the newly created files will be modified.

Next, let’s take a look at how to set umask in Golang. Golang provides the os package to operate files and directories. In the os package, we can use the syscall.Umask() function to set the default permission mask for file creation. The specific usage is as follows:

package main

import (
    "fmt"
    "syscall"
)

func main() {
    oldmask := syscall.Umask(002)
    defer syscall.Umask(oldmask)

    // create file or directory
}

In the above example, we use the Umask() function to set a new default permission mask and save the old umask value. After the file or directory is created, we use the defer statement to reset the previous umask value.

Through the above code, we can set the default permission mask when the Golang program is running. This is very useful during development, especially in applications involving multi-user, multi-tasking. We can set a different default permission mask for each task to ensure that the task gets the correct permissions when creating the file.

Of course, you must be cautious when setting the umask value. An umask value that is too loose may cause sensitive data to be used maliciously, while an umask value that is too conservative may limit the normal operation of the program. Therefore, the umask value needs to be set according to the actual situation and needs to ensure the safety and normal operation of the program.

The above is an introduction to setting umask in Golang. I hope it will be helpful to you.

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