ValueError: embedded null byte while using os.popen().read()

Question

i'm trying to pipe some lines with icons to rofi but i'm getting this errror and i don't understand why

def show_podcasts(f):
    podcasts_list = ""
    with open(f,"r") as podcasts:
        for line in podcasts:
            episode_title = " ".join(line.split(" ")[:-2])
            found = False
            for pic in os.listdir("images"):
                if os.path.isfile(os.path.join("images",pic)):
                    if pic.startswith(episode_title):
                        found = True
                        podcasts_list += episode_title + "\x00icon\x1f" + pic + "\n"
            if not found:
                podcasts_list += episode_title + "\n"
    print(podcasts_list)
    selected_podcast = os.popen("(cat << EOF\n" + podcasts_list + "EOF\n)| rofi -dmenu -p 'enter the podcast you are looking for'").read()

and this is the error


Traceback (most recent call last):
  File "/home/javier/ssd/dev/python/pod-rofi/main.py", line 91, in <module>
    main()
  File "/home/javier/ssd/dev/python/pod-rofi/main.py", line 84, in main
    show_podcasts("podcasts")
  File "/home/javier/ssd/dev/python/pod-rofi/main.py", line 77, in show_podcasts
    selected_podcast = os.popen("(cat << EOF\n" + podcasts_list + "EOF\n)| rofi -dmenu -p 'enter the podcast you are looking for'").read()
  File "/usr/lib/python3.10/os.py", line 985, in popen
    proc = subprocess.Popen(cmd,
  File "/usr/lib/python3.10/subprocess.py", line 966, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.10/subprocess.py", line 1775, in _execute_child
    self.pid = _posixsubprocess.fork_exec(
ValueError: embedded null byte

score 0 · Answer 1 · answered Apr 19 '22 at 13:10

I don't understand what exactly you want to do, but hope it helps if I explain the error.

Running a program involves a system call and the interface follows the C-language rule that a string (in this case the command) is terminated by a null-byte. The rule implies that a null byte cannot be one of the characters.

But here gets the null byte inserted:

podcasts_list += episode_title + "\x00icon\x1f" + ....
#                                 ^^^^

ValueError: embedded null byte while using os.popen().read()

1 Answers1