CGI Bash脚本生成守护进程

Question

I am working on a project to stream HDTV from a personal computer to devices supporting HTTP Live Streaming (think iOS devices and some android). I have the formatting of the video and the streaming aspects down. What I am now trying to implement is an easy way to change the channel remotely.

My current method involves connecting via SSH to kill the old stream and begin a new stream. This works, but isn't pretty. I want something my Mom or girlfriend could use. I decided I would build an HTML5 app that would issue the channel switching over CGI scripts. I currently have a parent process with a form that calls a child process to decide if the stream is running and then a subchild process to actually tune the stream.

As I am streaming live video from my computer I need the subchild process to run indefinitely. Unfortunately it seems that when my parent process is finished the background process started in the subchild process terminates.

I have tried a simple &, using nohup, setsid, and daemon. daemon runs cleanest but still terminates when the parent finishes. even with a -r flag. I'll place my code below and maybe someone will have an idea on how I could implement this or a better way to achieve the same thing? Thanks! (oh and i know killing vlc is not a pretty way to kill the stream, if you have a better way i'm all ears)

parent invoking child:
----------------------
./ChangeChannel.sh $channel     #passed from form submission


child (ChangeChannel.sh):
-------------------------
#!/bin/bash

directory=./Channels/
newchannel=$1

if [ $(pidof vlc) ]
    then
        sudo kill $(pidof vlc)
fi
daemon -r -v -d $directory$newchannel &


subchild example:
-----------------
vlc atsc://frequency=605029000 --intf=dummy --sout-transcode-audio-sync :live-cache=3000 --sout='#transcode{vcodec=h264,vb=150,fps=25,width=480,scale=1,venc=x264{aud,profile=baseline,level=30,keyint=15,bframes=0,ref=1},acodec=aac,ab=40,channels=2,samplerate=22050}:duplicate{dst=std{mux=ts,dst=-,access=livehttp{seglen=16,delsegs=true,numsegs=10,index=/var/www/stream/live.m3u8,index-url=content/live-######.ts},mux=ts{use-key-frames},dst=/var/www/stream/content/live-######.ts,ratecontrol=true}}'

how can i keep the subchild from terminating??? Running Apache on Ubuntu 12.04

Answer 1

I got it!

For anyone interested in how, i changed my tactics to use nohup, &, disown, and > /dev/null 2>&1.

Honestly, still not quite sure how I got it working... just a lot of trial and error with some educated guesses. My code follows:

parent invocation:
------------------
nohup ./ChangeChannel.sh $channel & disown


child invocation:
-----------------
sudo nohup su user $directory$newchannel &> /dev/null 2>&1


subchild invocation:
--------------------
vlc atsc://frequency=605029000 --intf=dummy --sout-transcode-audio-sync :live-cache=3000 --sout='#transcode{vcodec=h264,vb=150,fps=25,width=480,scale=1,venc=x264{aud,profile=baseline,level=30,keyint=15,bframes=0,ref=1},acodec=aac,ab=40,channels=2,samplerate=22050}:duplicate{dst=std{mux=ts,dst=-,access=livehttp{seglen=16,delsegs=true,numsegs=10,index=/var/www/stream/live.m3u8,index-url=content/live-######.ts},mux=ts{use-key-frames},dst=/var/www/stream/content/live-######.ts,ratecontrol=true}}' & disown

ChangeChannel.sh uses sudo to execute su via cgi in order to execute vlc as user other than root. It seems a little messy but hell it works.