diff --git a/tail.go b/tail.go index f3c6934..247fac1 100644 --- a/tail.go +++ b/tail.go @@ -211,10 +211,17 @@ func (tail *Tail) tailFileSync() { // Read line by line. for { + // grab the position in case we need to back up in the event of a half-line + offset, err := tail.Tell() + if err != nil { + tail.Kill(err) + return + } + line, err := tail.readLine() // Process `line` even if err is EOF. - if err == nil || (err == io.EOF && line != "") { + if err == nil { cooloff := !tail.sendLine(line) if cooloff { // Wait a second before seeking till the end of @@ -236,8 +243,22 @@ func (tail *Tail) tailFileSync() { } } else if err == io.EOF { if !tail.Follow { + if line != "" { + tail.sendLine(line) + } return } + + if tail.Follow && line != "" { + // this has the potential to never return the last line if + // it's not followed by a newline; seems a fair trade here + err := tail.seekTo(SeekInfo{Offset: offset, Whence: 0}) + if err != nil { + tail.Kill(err) + return + } + } + // When EOF is reached, wait for more data to become // available. Wait strategy is based on the `tail.watcher` // implementation (inotify or polling). @@ -317,7 +338,11 @@ func (tail *Tail) openReader() { } func (tail *Tail) seekEnd() error { - _, err := tail.file.Seek(0, 2) + return tail.seekTo(SeekInfo{Offset: 0, Whence: 2}) +} + +func (tail *Tail) seekTo(pos SeekInfo) error { + _, err := tail.file.Seek(pos.Offset, pos.Whence) if err != nil { return fmt.Errorf("Seek error on %s: %s", tail.Filename, err) }