Turn on grep‘s line buffering mode when using BSD grep (FreeBSD, Mac OS X etc.) tail -f file | grep –line-buffered my_pattern It looks like a while ago –line-buffered didn’t matter for GNU grep (used on pretty much any Linux) as it flushed by default (YMMV for other Unix-likes such as SmartOS, AIX or QNX). … Read more
Non Blocking If you are on linux (as windows does not support calling select on files) you can use the subprocess module along with the select module. import time import subprocess import select f = subprocess.Popen([‘tail’,’-F’,filename],\ stdout=subprocess.PIPE,stderr=subprocess.PIPE) p = select.poll() p.register(f.stdout) while True: if p.poll(1): print f.stdout.readline() time.sleep(1) This polls the output pipe for new … Read more
This may be quicker than yours. Makes no assumptions about line length. Backs through the file one block at a time till it’s found the right number of ‘\n’ characters. def tail( f, lines=20 ): total_lines_wanted = lines BLOCK_SIZE = 1024 f.seek(0, 2) block_end_byte = f.tell() lines_to_go = total_lines_wanted block_number = -1 blocks = [] … Read more