fileoutput.go

package main

import (
	"log"
	"os"
	"time"
)

type fileOutputPrivate struct {
	fd *os.File
}

func newFileOutputDesc() *outputDesc {
	return &outputDesc{
		open:      fileOutputOpen,
		sendStart: fileOutputSendStart,
		private:   new(fileOutputPrivate),
	}
}

/*
 * "The action
 *      =file
 *  replaces the contents of file with (the first 1000 bytes of) each selected line,
 *  padded with newlines to 1001 bytes. There is no protection of file against power outages."
 */
func fileOutputSendStart(sc *scriptLine, buf []byte) {
	buf2 := make([]byte, 0, 1001)
	if sc.timestamp != tsNone {
		buf2 = append(buf2, curFormattedTimestamp...)
		buf2 = append(buf2, ' ')
	}
	for _, c := range buf {
		if len(buf2) == 1000 {
			break
		}
		buf2 = append(buf2, c)
	}
	for len(buf2) < 1000 {
		buf2 = append(buf2, '\n')
	}
	buf2 = append(buf2, '\n')

	priv := (*fileOutputPrivate)(sc.desc.private.(*fileOutputPrivate))

	for {
		_, err := priv.fd.Seek(0, 0)
		if err == nil {
			break
		}
		log.Printf("unable to seek in %s, pausing: %v\n", sc.target, err)
		time.Sleep(time.Second)
	}
	writeLoop(sc.target, priv.fd, buf2)
}

func fileOutputOpen(sc *scriptLine) {
	priv := (*fileOutputPrivate)(sc.desc.private.(*fileOutputPrivate))
	for {
		fd, err := os.OpenFile(sc.target, os.O_WRONLY|os.O_CREATE, 0644)
		if err == nil {
			priv.fd = fd
			closeOnExec(fd)
			return
		}
	}
}