go - Check if there is something to read on STDIN in Golang

Question

I need a command line utility to behave different if some string is piped into its STDIN. Here's some minimal example:

package main // file test.go

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    bytes, _ := ioutil.ReadAll(os.Stdin)

    if len(bytes) > 0 {
        fmt.Println("Something on STDIN: " + string(bytes))
    } else {
        fmt.Println("Nothing on STDIN")
    }
}

This works fine if you call it like that:

echo foo | go run test.go

If test.go is called without anything on STDIN, the thing stucks at...

bytes, _ := ioutil.ReadAll(os.Stdin)

... waiting for EOF.

What do I need to do to get this going?

Thanks in advance!

question from:https://stackoverflow.com/questions/22744443/check-if-there-is-something-to-read-on-stdin-in-golang

Answer 1

I solved this by using os.ModeCharDevice:

stat, _ := os.Stdin.Stat()
if (stat.Mode() & os.ModeCharDevice) == 0 {
    fmt.Println("data is being piped to stdin")
} else {
    fmt.Println("stdin is from a terminal")
}