golang monitor cmd output

Question

I want to monitor a process status. The task is almost like this. t.py just outputs a number every second and I want to use test.go to store this number into a file. Unfortunately, the following code cannot do the job.

t.py:

import time
from sys import stdout

i=0
while 1:
    print("%d" % i) 
    time.sleep(1)
    i += 1

test.go

import (
    "bufio"
    "fmt"
    "os"
    "os/exec"
)

func main() {
    cmd := exec.Command("python", "t.py")
    stdout, err := cmd.StdoutPipe()
    if err != nil {
        fmt.Println(err)
    }
    scanner := bufio.NewScanner(stdout)
    err = cmd.Start()
    if err != nil {
        fmt.Println(err)
    }
    for scanner.Scan() {
        line := scanner.Text()
        f, _ := os.Create("./temp.txt")
        fmt.Fprintf(f, "then %s\n", line)
        f.Close()
    }
}

mattn · Accepted Answer · 2015-01-19 10:00:38Z

2

Output is buffered. Add stdout.flush() after print

import time
from sys import stdout

i=0
while 1:
    print("%d" % i) 
    stdout.flush()
    time.sleep(1)
    i += 1

answered Jan 19, 2015 at 10:00

mattn

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