def prep_subprocess(args=[], pipe_read=None, pipe_write=None):
''' Return a process object that read can execute.'''
p = Process()
new_in_fpath = None
new_out_fpath = None
try: # check for < > file redirection
index = 0
while index < len(args):
arg = args[index]
if arg == '<':
if pipe_read:
raise IndexError # TODO Multiple redirection error
new_in_fpath = args[index + 1]
index += 2
elif arg == '>':
if pipe_write:
raise IndexError # TODO Multiple redirection error
new_out_fpath = args[index + 1]
index += 2
else:
p.args.append(arg)
index += 1
except IndexError:
os.write(2, ("Shelly: Unexpected redirection %s \n" % args).encode())
return None
if new_in_fpath:
p.input= os.open(new_in_fpath, os.O_RDONLY)
os.set_inheritable(p.input, True)
else:
p.input = pipe_read
if new_out_fpath:
p.output = os.open(new_out_fpath, os.O_WRONLY | os.O_CREAT)
os.set_inheritable(p.output, True)
else:
p.output = pipe_write
return p
