Reading length of piped input to Go command line program

Question

I have the following code from Determine if Stdin has data with Go

package main

import (
    "fmt"
    "os"
)

func main() {
    file := os.Stdin
    fi, err := file.Stat()
    if err != nil {
        fmt.Println("file.Stat()", err)
    }
    size := fi.Size()
    if size > 0 {
        fmt.Printf("%v bytes available in Stdin\n", size)
    } else {
        fmt.Println("Stdin is empty")
    }
}

but no matter how I run it, size is always 0.

I am running Fedora 32 with Go version 1.14

A pipe doesn’t have a length. If you want to know the size you ha e to read it. — JimB, Jul 24 '20 at 00:43
@DBWizz: It doesn't work in your case because there is no standard way to read the size of a named pipe (semantically a pipe has no size, implementations vary by buffer size). Even if you are on a system that returns a size for the pipe, it's only going to report up to the internal buffer size which doesn't tell you the size of the input. — JimB, Jul 24 '20 at 13:27
@jimB I copied code from the web that others said worked for them. — DB Wizz, Jul 25 '20 at 05:01
@DBWizz: unfortunately not everything published on the internet is correct. `<< — JimB, Jul 27 '20 at 13:41

score -1 · Answer 1 · answered Jul 24 '20 at 03:12

-1

You have to compile to code to get an executable. Then you can pipe in any text to it, to get its size.

go build pipe.go
ls -lah pipe
2.1M Jul 23 23:06 pipe

Then you can run it by

echo "test" | ./pipe
5 bytes available in Stdin

answered Jul 24 '20 at 03:12

Saeed

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Can you please share what you get when you run `go build pipe.go` and `echo "test" | ./pipe` ? – Saeed Jul 24 '20 at 11:29
1

I get "0 bytes available in Stdin" – DB Wizz Jul 25 '20 at 04:58

Reading length of piped input to Go command line program

1 Answers1