87 lines
2.4 KiB
Go
87 lines
2.4 KiB
Go
// Sometimes our Go programs need to spawn other, non-Go
|
|
// processes.
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"io"
|
|
"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")
|
|
|
|
// The `Output` method runs the command, waits for it
|
|
// to finish and collects its standard 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))
|
|
|
|
// `Output` and other methods of `Command` will return
|
|
// `*exec.Error` if there was a problem executing the
|
|
// command (e.g. wrong path), and `*exec.ExitError`
|
|
// if the command ran but exited with a non-zero return
|
|
// code.
|
|
_, err = exec.Command("date", "-x").Output()
|
|
if err != nil {
|
|
switch e := err.(type) {
|
|
case *exec.Error:
|
|
fmt.Println("failed executing:", err)
|
|
case *exec.ExitError:
|
|
fmt.Println("command exit rc =", e.ExitCode())
|
|
default:
|
|
panic(err)
|
|
}
|
|
}
|
|
|
|
// 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, _ := io.ReadAll(grepOut)
|
|
grepCmd.Wait()
|
|
|
|
// We omitted error checks in the above example, but
|
|
// you could use the usual `if err != nil` pattern for
|
|
// all of them. We also only collect the `StdoutPipe`
|
|
// results, but you could collect the `StderrPipe` in
|
|
// exactly the same way.
|
|
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))
|
|
}
|