{"id":24664,"date":"2020-05-05T10:11:00","date_gmt":"2020-05-05T08:11:00","guid":{"rendered":"https:\/\/pi3g.com\/?p=24664"},"modified":"2020-05-05T10:11:00","modified_gmt":"2020-05-05T08:11:00","slug":"termishell-a-web-based-shell-for-the-raspberry-pi-development-notes","status":"publish","type":"post","link":"https:\/\/pi3g.com\/de\/termishell-a-web-based-shell-for-the-raspberry-pi-development-notes\/","title":{"rendered":"TermiShell: eine webbasierte Shell f\u00fcr den Raspberry Pi (Entwicklungsnotizen)"},"content":{"rendered":"

Introduction<\/h1>\n

In the course of development of PiCockpit<\/a>, I am going to add a web-based Terminal called TermiShell<\/strong>.<\/p>\n

\"image\"<\/a><\/p>\n

TermiShell icon, by: <\/em>Stephanie Harvey<\/em><\/a> via unsplash.com <\/em><\/p>\n

TermiShell is going to allow you to log into your Raspberry Pi using PiCockpit.com (and the picockpit-client) \u2013 no additional application required on either side. This should be very comfortable, especially when on the go.<\/p>\n

TermiShell is not going to be released in the upcoming v2.0 release of PiCockpit<\/strong>, because it requires additional preparation work, and would delay the upcoming release significantly. I would also rather not cut corners on security (which would be the alternative to make it work right away). <\/p>\n

The work, however, will positively impact many other capabilities of PiCockpit as well \u2013 for instance the ability to stream video (from the Pi camera), file uploads \/ downloads from the Pi, and many other functionalities which require data streams.<\/p>\n

I am compiling information for myself, and also for other interested developers about my thoughts on how to realize such a web-based terminal, and background information.<\/p>\n

What is a pseudo-terminal (pty)?<\/h1>\n

Python offers built-in functionalities to execute processes, and to capture their output (stdout and stderr) and send them input (stdin).<\/p>\n

Here is a first attempt with subprocess:<\/p>\n

\n

# dow, day of work 1.5.2020
\nimport os
\nimport sys
\nimport time
\nimport threading
\nimport contextlib
\nimport subprocess<\/p>\n

print(“Hello world!”)
\nprint(“Running omxplayer”)<\/p>\n

\ndef output_reader(proc):
     contFlag = True
     while contFlag:
         chars = proc.stdout.read(1)
         if chars != None:
             if chars != b”:
                 print(chars.decode(‘utf-8’), end=””, flush=True)
             else:
                 contFlag = False<\/p>\n

\nproc = subprocess.Popen(
     [‘omxplayer’, ‘\/home\/pi\/thais.mp4’],
     stdin=subprocess.PIPE,
     stdout=subprocess.PIPE,
     stderr=subprocess.PIPE,
     bufsize=0)<\/p>\n

t = threading.Thread(target=output_reader, args=(proc,))
\nt.start()<\/p>\n

sys.stdin = os.fdopen(sys.stdin.fileno(), ‘rb’, buffering=0)<\/p>\n

while True:
     char = sys.stdin.read(1)
     print(char.decode(‘utf-8’), end=””, flush=True)
     proc.stdin.write(char)<\/p>\n

proc.stdin.write(b’z’)<\/p>\n

t.join()<\/p>\n<\/blockquote>\n

Please note the following in the code above (which is not perfect, just demo code \u2013 and in fact might not work as expected!):<\/p>\n