GO lang : Communicate with shell process - process

Question

I want to execute a shell script from Go.
The shell script takes standard input and echoes the result.
I want to supply this input from GO and use the result.
What I am doing is:
cmd := exec.Command("python","add.py")
in, _ := cmd.StdinPipe()
But how do I read from in?

Answer 1

Here is some code writing to a process, and reading from it:
package main
import (
"bufio"
"fmt"
"os/exec"
)
func main() {
// What we want to calculate
calcs := make([]string, 2)
calcs[0] = "3*3"
calcs[1] = "6+6"
// To store the results
results := make([]string, 2)
cmd := exec.Command("/usr/bin/bc")
in, err := cmd.StdinPipe()
if err != nil {
panic(err)
}
defer in.Close()
out, err := cmd.StdoutPipe()
if err != nil {
panic(err)
}
defer out.Close()
// We want to read line by line
bufOut := bufio.NewReader(out)
// Start the process
if err = cmd.Start(); err != nil {
panic(err)
}
// Write the operations to the process
for _, calc := range calcs {
_, err := in.Write([]byte(calc + "\n"))
if err != nil {
panic(err)
}
}
// Read the results from the process
for i := 0; i < len(results); i++ {
result, _, err := bufOut.ReadLine()
if err != nil {
panic(err)
}
results[i] = string(result)
}
// See what was calculated
for _, result := range results {
fmt.Println(result)
}
}
You might want to read/write from/to the process in different goroutines.