Golang : Pipe output from one os.Exec(shell command) to another command

Problem :

You want to execute one shell command with os.Exec() function, wait for it to complete and then pipe the output to another shell command. In Unix/Linux, this is something similar to... for example:

 ls | wc -l

Solution :

Use the io.Pipe() function to pipe output from the first executed command to the second executing command. For example :

 package main

 import (
 "bytes"
 "io"
 "os/exec"
 "fmt"
 )


 func main() {
 first := exec.Command("ps", "-ef")
 second := exec.Command("wc", "-l")

 // http://golang.org/pkg/io/#Pipe

 reader, writer := io.Pipe()

 // push first command output to writer
 first.Stdout = writer

 // read from first command output
 second.Stdin = reader

 // prepare a buffer to capture the output
 // after second command finished executing
 var buff bytes.Buffer
 second.Stdout = &buff

 first.Start()
 second.Start()
 first.Wait()
 writer.Close()
 second.Wait()

 total := buff.String() // convert output to string

 fmt.Printf("Total processes running : %s", total)

 }

Sample output :

Total processes running : 89

Reference :

http://golang.org/pkg/io/#Pipe