Read (os.read) FIFO non-blockingly without fixed buffer size - python-2.7

Question

In this question, the asker has addressed the problem of reading from a named pipe in a non-blocking manner, but he uses a fixed buffer size. Is there a way to do this without a fixed buffer size and just waiting for the other end to terminate their own buffer with a newline character?

Answer 1

Assuming that your delimiter is a you can read multiple variable length strings in a non-blocking manner, as shown in this program which counts while receiving output from a named pipe.
import os
import time
import errno
import sys
io = os.open(expanduser("~/named_pipes/cob_input"), os.O_RDONLY | os.O_NONBLOCK)
# For implementing non-blocking IO
def read_pipe_non_blocking(input_pipe, size):
try:
in_buffer = os.read(input_pipe, size)
except OSError as err:
if err.errno == errno.EAGAIN or err.errno == errno.EWOULDBLOCK:
in_buffer = None
else:
raise # something else has happened -- better reraise
return in_buffer
def get_azimuth(input_pipe):
in_buffer = read_pipe_non_blocking(input_pipe, 1)
print(in_buffer)
if(in_buffer is None):
sys.stderr.write("n")
return ""
else:
tmp_buffer = None
while(tmp_buffer != "a"):
sys.stderr.write("m")
time.sleep(0.1)
tmp_buffer = read_pipe_non_blocking(input_pipe, 1)
if(tmp_buffer != None and tmp_buffer != "a"):
in_buffer += tmp_buffer
read_pipe_non_blocking(input_pipe, 1) #Read in the newline character and the toss it
sys.stderr.write("\nReturning \{%s\}" %in_buffer)
return in_buffer
i = 0
while 1:
print i
time.sleep(1)
i += 1
get_azimuth(io)
This code has been directly copy pasted from my code and isn't really that clear. If anyone needs clarification, leave a comment.