v0.6.2 : Write to output file, SIGUSR1 will reopen output file so we can newsyslog

main.go

@@ -27,13 +27,16 @@ import (
 	"io"
 	"os"
 	"fmt"
+	"sync"
 	"bufio"
 	"strings"
+	"syscall"
+	"os/signal"
 	"github.com/spf13/pflag"
 )
 
 const (
-	version = "0.6.1"
+	version = "0.6.2"
 )
 
 var (
@@ -42,19 +45,43 @@ var (
 
 	// Default delimiter
 	delimiter = ","
+
+	Writer *bufio.Writer
 )
 
+func NewWriter(file string) (*bufio.Writer, *os.File, error) {
+	if len(file) > 0 {
+		var f *os.File
+		var err error
+
+		f, err = os.OpenFile(file, os.O_CREATE|os.O_WRONLY, 0640)
+		if err != nil {
+			return nil, nil, err
+		}
+		Writer = bufio.NewWriter(f)
+		return Writer, f, nil
+	} else {
+		Writer = bufio.NewWriter(os.Stdout)
+		return Writer, nil, nil
+	}
+}
+
 func main() {
 	var flags int
 	var oneLine bool
 	var noUserResolve bool
 	var syslog23 bool
 	var json bool
+	var outputFile string
+	// Output file mutex
+	var outfMtx sync.Mutex
+	var outFile *os.File
 
 	pflag.BoolVarP(&oneLine, "oneline", "l", false, "Prints the entire record on the same line")
 	pflag.BoolVarP(&noUserResolve, "numeric", "n", false, "Do not convert user and group IDs to their names but leave in their numeric forms")
 	pflag.BoolVarP(&json, "json", "j", false, "Print compact json")
 	pflag.BoolVarP(&syslog23, "syslog23", "s", false, "Print time as \"2006-01-02T15:04:05.000Z07:00\", RFC339 with ms, also used on RSYSLOG_SyslogProtocol23Format. \"msec\" field will not be print in json output")
+	pflag.StringVarP(&outputFile, "out", "o", "", "Output to file, overwrite existing. File will be re-opened receiving SIGUSR1.")
 	pflag.BoolVarP(&showVersion, "version", "V", false, "Show version and exit")
 
 	var Usage = func() {
@@ -90,9 +117,35 @@ func main() {
 	}
 	filename := args[len(args)-1]
 
+	// Get a writer, file or stdout
+	_, outFile, err := NewWriter(outputFile)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	if len(outputFile) > 0 {
+		// Manage output file rotation when receiving SIGUSR1
+		sig := make(chan os.Signal)
+		signal.Notify(sig, syscall.SIGUSR1)
+		go func() {
+			for {
+				<-sig
+				outfMtx.Lock()
+				fmt.Println("SIGUSR1 received, recreating output file")
+				outFile.Close()
+				_, outFile, err = NewWriter(outputFile)
+				if err != nil {
+					outfMtx.Unlock()
+					fmt.Fprintf(os.Stderr, "%v\n", err)
+					os.Exit(1)
+				}
+				outfMtx.Unlock()
+			}
+		}()
+	}
+
 	var f *os.File
 	var r *bufio.Reader
-	var err error
 	if len(filename) > 0 {
 		// If arg is "-", open stdin to read content
 		if true == strings.EqualFold(filename, "-") {
@@ -100,13 +153,12 @@ func main() {
 		} else {
 			f, err = os.Open(filename)
 			if err != nil {
-				fmt.Printf("Impossible d'ouvrir le fichier %s\n", filename)
+				fmt.Fprintf(os.Stderr, "Impossible d'ouvrir le fichier %s\n", filename)
 				os.Exit(-1)
 			}
 			r = bufio.NewReader(f)
 		}
 
-		//for i := 0 ; i < 20 ; i++ {
 		for {
 			rec, err := readRecordToStruct(r)
 			if err != nil {
@@ -116,7 +168,21 @@ func main() {
 					return
 				}
 			}
-			rec.Print(os.Stdout, ",", flags)
+			if len(outputFile) > 0 {
+				outfMtx.Lock()
+				rec.Print(Writer, ",", flags)
+				Writer.Flush()	// Performance ?
+				outfMtx.Unlock()
+			} else {
+				// No need for mutex with stdout
+				rec.Print(Writer, ",", flags)
 			}
 		}
+	}
+
+	if len(outputFile) > 0 && outFile != nil {
+		outfMtx.Lock()
+		outFile.Close()
+		outfMtx.Unlock()
+	}
 }