Add --exec-before and --exec-after options

* Adds a pair of additional, optional, parameters --exec-before and
  --exec-after which both take a path to a local executable that gets
  run before the download starts, or after it completes respectively.
  The executable will be passed the completed filename as the first argument
  with the URL as the second.

README.md

@@ -73,6 +73,10 @@ Options:
 	--error
 		Print only errors and general information.
 
+	--exec-path COMMAND_PATH
+		Execute the given COMMAND_PATH after a completed download.
+		The first argument to COMMAND_PATH will be the completed filename.
+
 	--ffmpeg-path FFMPEG_PATH
 		Set a specific ffmpeg location, including program name.
 		e.g. "C:\ffmpeg\ffmpeg.exe" or "/opt/ffmpeg/ffmpeg"

main.go

@@ -72,10 +72,18 @@ Options:
 	--add-metadata
 		Write some basic metadata information to the final file.
 
+	--after-exec-path COMMAND_PATH
+		Execute the given COMMAND_PATH after a completed download.
+		The first argument to COMMAND_PATH will be the completed filename.
+
 	--audio-url GOOGLEVIDEO_URL
 		Pass in the given url as the audio fragment url. Must be a
 		Google Video url with an itag parameter of 140.
 
+	--before-exec-path COMMAND_PATH
+		Execute the given COMMAND_PATH before a download is started.
+		The first argument to COMMAND_PATH will be the target filename.
+
 	-c
 	--cookies COOKIES_FILE
 		Give a cookies.txt file that has your youtube cookies. Allows
@@ -394,6 +402,8 @@ var (
 	gvVideoUrl        string
 	tempDir           string
 	ffmpegPath        string
+	execBefore        string
+	execAfter         string
 	proxyUrl          *url.URL
 	threadCount       uint
 	fragMaxTries      uint
@@ -499,6 +509,8 @@ func init() {
 	cliFlags.StringVar(&tempDir, "td", "", "Temporary directory for downloading files.")
 	cliFlags.StringVar(&tempDir, "temporary-dir", "", "Temporary directory for downloading files.")
 	cliFlags.StringVar(&ffmpegPath, "ffmpeg-path", "ffmpeg", "Specify a custom ffmpeg program location, including program name.")
+	cliFlags.StringVar(&execBefore, "exec-before", "", "Execute this command before a download starts.")
+	cliFlags.StringVar(&execAfter, "exec-after", "", "Execute this command after a download completes.")
 	cliFlags.IntVar(&retrySecs, "r", 0, "Seconds to wait between checking stream status.")
 	cliFlags.IntVar(&retrySecs, "retry-stream", 0, "Seconds to wait between checking stream status.")
 	cliFlags.UintVar(&threadCount, "threads", 1, "Number of download threads for each stream type.")
@@ -559,6 +571,16 @@ func init() {
 	})
 }
 
+func ExecCallback(execPath string, execArgs []string) {
+	if execPath != "" {
+		LogGeneral("Attempting to call execute exec-before/after COMMAND_PATH")
+		eRetcode := Execute(execPath, execArgs)
+		if eRetcode != 0 {
+			LogError("Execute returned code %d. Something must have gone wrong with %s.", eRetcode, execPath)
+		}
+	}
+}
+
 // ehh, bad way to do this probably but allows deferred functions to run
 // while also allowing early return with a non-0 exit code.
 func run() int {
@@ -865,12 +887,14 @@ func run() int {
 	if len(info.GetDownloadUrl(DtypeAudio)) > 0 {
 		LogInfo("Starting download to %s", afile)
 		go info.DownloadStream(DtypeAudio, afile, progressChan, dlDoneChan)
+		ExecCallback(execBefore, []string{finalAudioFile, info.URL})
 		activeDownloads += 1
 	}
 
 	if len(info.GetDownloadUrl(DtypeVideo)) > 0 {
 		LogInfo("Starting download to %s", vfile)
 		go info.DownloadStream(DtypeVideo, vfile, progressChan, dlDoneChan)
+		ExecCallback(execBefore, []string{finalVideoFile})
 		activeDownloads += 1
 	}
 
@@ -1119,6 +1143,8 @@ func run() int {
 		LogGeneral("%[1]sFinal audio file: %[2]s%[1]s", "\n", audioFFMpegArgs.FileName)
 	}
 
+	ExecCallback(execAfter, []string{ffmpegArgs.FileName, info.URL})
+
 	return 0
 }