Read file info in Golang
In this article, we are going to show you how to read files or directory info in Golang. When it comes to security it is very important to determine who is the owner, last changed, and if the file contains hidden files. Hackers nowadays are notorious for leaving malicious files that can affect your computer.
In order to read the file, we need to use the os.Stat() function which returns the file metadata. Such information is provided through a FileInfo struct.
fileInfo, err := os.Stat("./golang/file_info/english/file_directory/file.txt")
if err != nil {
log.Fatal(err)
}From the FileInfo struct all additional file properties can be extracted. The Name() function returns the file name.
fmt.Println("File name: ", fileInfo.Name())The Size() returns the file size in bytes. To make it much easier to read in our example, we create an additional function that returns the file size in a string format. It expects a FileInfo struct and calculate the size and returns it in bytes, kilobytes, or megabytes (depends on the calculation).
func getFileSize(fileInfo fs.FileInfo) string {
size := fileInfo.Size()
if size < 1000 { // File is in bytes
return fmt.Sprintf("%d bytes", size)
} else { // else file size is in kilobytes or megabytes
fileSizeInKb := float64(size) / float64(1000)
if fileSizeInKb > 1000 { // file size is in megabytes
fileSizeInMb := fileSizeInKb / float64(1000)
return fmt.Sprintf("%d Mb", fileSizeInMb)
} else { // file size is in kilobytes
return fmt.Sprintf("%d Kb", fileSizeInKb)
}
}
}
To determine the file permission, the Mode() function can be used. The function returns a FileMode struct that represents a file’s mode and permission bits. Not all bits are applied to all Operating systems.
fmt.Println("Permissions: ", directoryInfo.Mode())For the last modification metadata, the ModTime() can be used that returns a Time struct.
fmt.Println("Last modified: ", directoryInfo.ModTime())In addition to the getFileSize function, another one is created to determine if a file is a directory. It returns the yes or no string.
func isDirectory(fileInfo fs.FileInfo) string {
var result = "No"
if fileInfo.IsDir() {
result = "yes"
}
return result
}fmt.Println("|----------- File info -----------|")
fmt.Println("File name: ", fileInfo.Name())
fmt.Println("Size: ", getFileSize(fileInfo))
fmt.Println("Permissions: ", fileInfo.Mode())
fmt.Println("Last modified: ", fileInfo.ModTime())
fmt.Println("Is Directory: ", isDirectory(fileInfo))
fmt.Println("|----------- File info -----------|\n")The code snippet shows a directory example.
directoryInfo, err := os.Stat("./golang/file_info/english/file_directory")
if err != nil {
log.Fatal(err)
}fmt.Println("|----------- Directory info -----------|")
fmt.Println("File name: ", directoryInfo.Name())
fmt.Println("Size: ", getFileSize(directoryInfo))
fmt.Println("Permissions: ", directoryInfo.Mode())
fmt.Println("Last modified: ", directoryInfo.ModTime())
fmt.Println("Is Directory: ", isDirectory(directoryInfo))
fmt.Println("|----------- Directory info -----------|")Program result:
|----------- File info -----------|
File name: file.txt
Size: 21 bytes
Permissions: -rw-r--r--
Last modified: 2022-01-09 17:26:32.81671206 -0400 AST
Is Directory: No
|----------- File info -----------|
|----------- Directory info -----------|
File name: file_directory
Size: 96 bytes
Permissions: drwxr-xr-x
Last modified: 2022-01-09 17:42:13.997886317 -0400 AST
Is Directory: yes
|----------- Directory info -----------|
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