Menu
I'm running nodejs on a raspberry pi and I want to run a child process to spawn a webcam stream.
Outside of node my command is:
raspivid -n -mm matrix -w 320 -h 240 -fps 18 -g 100 -t 0 -b 5000000 -o - | ffmpeg -y -f h264 -i - -c:v copy -map 0:0 -f flv -rtmp_buffer 100 -rtmp_live live "rtmp://example.com/big/test"
With child_process I have to break each argument up
var args = ["-n", "-mm", "matrix", "-w", "320", "-h", "240", "-fps", "18", "-g", "100", "-t", "0", "-b", "5000000", "-o", "-", "|", "ffmpeg", "-y", "-f", "h264", "-i", "-", "-c:v", "copy", "-map", "0:0", "-f", "flv", "-rtmp_buffer", "100", "-rtmp_live", "live", "rtmp://example.com/big/test"];
camera.proc = child.spawn('raspivid', args);
However it chokes on the | character:
error, exit code 64
Invalid command line option (|)
How do I use this pipe character as an argument?
523
js allows single-threaded, non-blocking performance but running a single thread in a CPU cannot handle increasing workload hence the child_process module can be used to spawn child processes. The child processes communicate with each other using a built-in messaging system.
Spawned Child Processes. The spawn function launches a command in a new process and we can use it to pass that command any arguments. For example, here's code to spawn a new process that will execute the pwd command. const { spawn } = require('child_process'); const child = spawn('pwd');
The exec() function in Node. js creates a new shell process and executes a command in that shell. The output of the command is kept in a buffer in memory, which you can accept via a callback function passed into exec() .
This has been answered in another question: Using two commands (using pipe |) with spawn
In summary, with child.spawn everything in args should be an argument of your 'raspivid' command. In your case, the pipe and everything after it are actually arguments for sh.
A workaround is to call child.spawn('sh', args) where args is:
var args = ['-c', <the entire command you want to run as a string>];
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
