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main.go
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main.go
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package main
import (
"flag"
"fmt"
"os"
"os/exec"
"path"
"time"
)
var (
flagSleep = flag.Duration("i", 30*time.Millisecond, "poll time")
flagRace = flag.Bool("race", false, "build with -race")
)
func main() {
flag.Parse()
if flag.NArg() == 0 {
fatal("need at least 1 argument: go file to watch")
}
watch(flag.Arg(0), flag.Args()[1:])
}
func watch(fname string, args []string) {
var ts time.Time
for {
time.Sleep(*flagSleep)
info, err := os.Stat(fname)
check(err)
if info.ModTime() != ts {
rerun(fname, args)
ts = info.ModTime()
}
}
}
var last *exec.Cmd
func rerun(fname string, args []string) {
if last != nil {
if err := last.Process.Kill(); err != nil {
fmt.Fprintln(os.Stderr, err)
}
if err := last.Wait(); err != nil {
fmt.Fprintln(os.Stderr, err)
}
}
if err := compile(fname); err != nil {
fmt.Fprintln(os.Stderr, err)
return
}
dir := path.Dir(fname)
base := path.Base(fname)
noExt := base[:len(base)-len(path.Ext(base))]
allArgs := append([]string{"-o", noExt + ".jpg"}, args...)
cmd := exec.Command("./"+noExt, allArgs...)
cmd.Dir = dir
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.Stdin = os.Stdin
if err := cmd.Start(); err != nil {
fmt.Fprintln(os.Stderr, err)
}
out, err := exec.Command("renice", "20", fmt.Sprint(cmd.Process.Pid)).CombinedOutput()
if err != nil {
fmt.Fprintf(os.Stderr, "renice: %s", out)
}
last = cmd
}
func compile(fname string) error {
dir := path.Dir(fname)
cmd := exec.Command("go", "build", "-race="+fmt.Sprint(*flagRace), path.Base(fname))
cmd.Dir = dir
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
cmd.Stdin = os.Stdin
return cmd.Run()
}
func check(e error) {
if e != nil {
fatal(e)
}
}
func fatal(x ...interface{}) {
fmt.Fprintln(os.Stderr, x...)
os.Exit(1)
}