How to get output from stdout into a string in golang

Question

I have the following code which outputs data from stdout to a file:

cmd := exec.Command("ls","lh")
outfile, err := os.Create("./out.txt")
if err != nil {
    panic(err)
}
defer outfile.Close()

stdoutPipe, err := cmd.StdoutPipe()
if err != nil {
    panic(err)
}

writer := bufio.NewWriter(outfile)
defer writer.Flush()

err = cmd.Start()
if err != nil {
    panic(err)
}

go io.Copy(writer, stdoutPipe)
cmd.Wait()

I need to get the output from stdout into a string value instead of a file. How do I achieve that?

Is there perhaps another function that will allow me to change the io.Copy line to go io.Copy(myStringVariable, stdoutPipe) as I need to read the output of the command and apply some processing to it?

Thanks in advance

You could have just assigned the file as the command's Stdout and avoided the pipe and copy goroutine (in which you were losing your read/write errors), — Mr_Pink
– Mr_Pink, Commented Sep 13, 2016 at 20:15

Mr_Pink · Accepted Answer · 2016-09-13 22:30:19Z

14

You don't need the pipe, writer, goroutine, etc. Just use Cmd.Output

out, err := exec.Command("ls","lh").Output()

You can convert the output []byte to a string as needed with string(out)

edited Sep 13, 2016 at 22:30

answered Sep 13, 2016 at 20:11

Mr_Pink

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1 Comment

Dean Over a year ago

Short and sweet! Thanks

Ilia Choly · Accepted Answer · 2016-09-13 20:21:07Z

6

You can set the file as the command's stdout

f, err := os.Create("./out.txt")
if err != nil {
    panic(err)
}
defer f.Close()

cmd := exec.Command("ls", "-lh")
cmd.Stdout = f
cmd.Stderr = os.Stderr

if err := cmd.Run(); err != nil {
    panic(err)
}

answered Sep 13, 2016 at 20:21

Ilia Choly

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