Golang : How to get Unix file descriptor for console and file
A short tutorial showing you how to obtain the Unix file descriptor for terminal/console and file in Golang with the os
package. Basically, there are 3 file descriptors under Unix/Linux environment :
- 0 for input
- 1 for output
- 3 for file
and knowing this information can be helpful in situation when you want to test if a given variable is a file or console.
Here we go!
package main
import (
"fmt"
"os"
)
func main() {
// get console unix file descriptor
outputFileDesc := int(os.Stdout.Fd())
outputName := os.Stdout.Name()
fmt.Println("Terminal or console output Unix file descriptor : ", outputFileDesc)
fmt.Println("output Unix file descriptor name : ", outputName)
fmt.Println("------------------------")
inputFileDesc := int(os.Stdin.Fd())
inputName := os.Stdin.Name()
fmt.Println("Terminal or console input Unix file descriptor : ", inputFileDesc)
fmt.Println("input Unix file descriptor name : ", inputName)
fmt.Println("------------------------")
// get a file unix file descriptor
file, err := os.Open("file.data")
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fileDescriptor := int(file.Fd()) // get the unix descriptor
fileDescriptorName := file.Name() // get the file name
file.Close()
fmt.Printf("%s Unix file descriptor : %d \n", fileDescriptorName, fileDescriptor)
}
Output :
Terminal or console output Unix file descriptor : 1
output Unix file descriptor name : /dev/stdout
------------------------
Terminal or console input Unix file descriptor : 0
input Unix file descriptor name : /dev/stdin
------------------------
file.data Unix file descriptor : 3
Happy coding!
References :
https://golang.org/pkg/os/#File.Fd
https://socketloop.com/references/golang-os-file-fd-function-example
http://www.theunixschool.com/2010/08/unix-file-descriptors.html
By Adam Ng
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