Spawn a Process
Examples
Filter
package main
import (
"fmt"
"io/ioutil"
"os/exec"
)
func main() {
// We’ll start with a simple command that takes no arguments or input and just prints something to stdout.
// The exec.Command helper creates an object to represent this external process.
dateCmd := exec.Command("date")
// .Output is another helper that handles the common case of running a command, waiting for it to finish, and collecting its output.
// If there were no errors, dateOut will hold bytes with the date info.
dateOut, err := dateCmd.Output()
if err != nil {
panic(err)
}
fmt.Println("> date")
fmt.Println(string(dateOut))
// Next we’ll look at a slightly more involved case where we pipe data to the external process
// on its stdin and collect the results from its stdout.
grepCmd := exec.Command("grep", "hello")
// Here we explicitly grab input/output pipes, start the process, write some input to it,
// read the resulting output, and finally wait for the process to exit.
grepIn, _ := grepCmd.StdinPipe()
grepOut, _ := grepCmd.StdoutPipe()
grepCmd.Start()
grepIn.Write([]byte("hello grep\ngoodbye grep"))
grepIn.Close()
grepBytes, _ := ioutil.ReadAll(grepOut)
grepCmd.Wait()
fmt.Println("> grep hello")
fmt.Println(string(grepBytes))
// Note that when spawning commands we need to provide an explicitly delineated command and argument array, vs. being able to just pass in one command-line string.
// If you want to spawn a full command with a string, you can use bash’s -c option:
lsCmd := exec.Command("bash", "-c", "ls -a -l -h")
lsOut, err := lsCmd.Output()
if err != nil {
panic(err)
}
fmt.Println("> ls -a -l -h")
fmt.Println(string(lsOut))
}