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| package main
import (
"flag"
"fmt"
"io"
"log"
"os"
"os/exec"
"os/signal"
"strings"
"sync"
"syscall"
)
var (
logFilePath = flag.String("log-file", "", "If non-empty, save stdout to this file")
alsoToStdOut = flag.Bool("also-stdout", false, "useful with log-file, log to standard output as well as the log file")
redirectStderr = flag.Bool("redirect-stderr", true, "treat stderr same as stdout")
logFile *os.File
logFileMu sync.Mutex
globalLogFile string
globalAlsoStdOut bool
globalRedirectStderr bool
)
type SyncWriter struct {
mu sync.Mutex
w io.Writer
}
func (sw *SyncWriter) Write(p []byte) (n int, err error) {
sw.mu.Lock()
defer sw.mu.Unlock()
return sw.w.Write(p)
}
func (sw *SyncWriter) SetWriter(w io.Writer) {
sw.mu.Lock()
defer sw.mu.Unlock()
sw.w = w
}
var (
outputSync = &SyncWriter{w: os.Stdout}
errSync = &SyncWriter{w: os.Stderr}
)
func main() {
flag.Parse()
if err := configureAndRun(); err != nil {
log.Fatal(err)
}
}
func configureAndRun() error {
globalLogFile = *logFilePath
globalAlsoStdOut = *alsoToStdOut
globalRedirectStderr = *redirectStderr
if globalLogFile != "" {
var err error
logFile, err = os.OpenFile(globalLogFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
return fmt.Errorf("failed to open log file: %w", err)
}
if globalAlsoStdOut {
outputSync.SetWriter(io.MultiWriter(os.Stdout, logFile))
} else {
outputSync.SetWriter(logFile)
}
if globalRedirectStderr {
errSync.SetWriter(outputSync)
}
}
args := flag.Args()
if len(args) == 0 {
return fmt.Errorf("not enough arguments to run")
}
exe := args[0]
var exeArgs []string
if len(args) > 1 {
exeArgs = args[1:]
}
cmd := exec.Command(exe, exeArgs...)
cmd.Stdout = outputSync
cmd.Stderr = errStream()
log.Printf("Running command:\n%v", cmdInfo(cmd))
err := cmd.Start()
if err != nil {
return fmt.Errorf("starting command: %w", err)
}
go setupSigHandler(cmd.Process)
if err := cmd.Wait(); err != nil {
return fmt.Errorf("running command: %w", err)
}
return nil
}
func errStream() io.Writer {
if *redirectStderr {
return outputSync
}
return os.Stderr
}
func cmdInfo(cmd *exec.Cmd) string {
return fmt.Sprintf(
`Command env: (log-file=%v, also-stdout=%v, redirect-stderr=%v)
Run from directory: %v
Executable path: %v
Args (comma-delimited): %v`, *logFilePath, *alsoToStdOut, *redirectStderr,
cmd.Dir, cmd.Path, strings.Join(cmd.Args, ","),
)
}
func setupSigHandler(process *os.Process) {
signals := []os.Signal{
syscall.SIGHUP, syscall.SIGINT,
syscall.SIGTERM, syscall.SIGQUIT, syscall.SIGUSR1,
}
c := make(chan os.Signal, 1)
signal.Notify(c, signals...)
log.Println("Now listening for signals")
for s := range c {
if s == syscall.SIGUSR1 {
handleLogRotate()
} else {
forwardSignal(process, s)
}
}
}
func handleLogRotate() {
logFileMu.Lock()
defer logFileMu.Unlock()
if globalLogFile == "" {
log.Println("No log file configured, ignoring SIGUSR1")
return
}
if logFile != nil {
logFile.Sync()
if err := logFile.Close(); err != nil {
log.Printf("Error closing log file: %v", err)
}
}
newFile, err := os.OpenFile(globalLogFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
log.Printf("ERROR: Failed to reopen log file: %v (logging to stdout)", err)
outputSync.SetWriter(os.Stdout)
if globalRedirectStderr {
errSync.SetWriter(os.Stdout)
}
return
}
logFile = newFile
log.SetOutput(logFile)
log.Println("Successfully reopened log file")
if globalAlsoStdOut {
outputSync.SetWriter(io.MultiWriter(os.Stdout, logFile))
} else {
outputSync.SetWriter(logFile)
}
if globalRedirectStderr {
errSync.SetWriter(outputSync)
}
}
func forwardSignal(process *os.Process, s os.Signal) {
log.Printf("Forwarding signal %v to PID %v", s, process.Pid)
if err := process.Signal(s); err != nil {
log.Printf("Error forwarding signal %v: %v", s, err)
}
}
|
