fflush

I am (re-)learning programming and I started with C. My IDE (if I may say so) is cygwin (32Bit) and Visual-Studio 2010 both on Windows7. I am always compiling the code I write with gcc (cygwin) as well as with the VS2010 compiler. I do so, I guess, because I think it is a good way of learning. Anyway I just learned about fflush(stdin), i.e. flushing the stdin buffer. Seems a good functionality because else, using scanf appears to be a pain. So I wrote the code below based on an example from my text book. It compiles both with gcc in cygwin as well as with VS2010. When I run the VS compiled

I don't understand why sometimes I need to use fflush() and sometimes not. My program is segfaulting at the moment and I am debugging it with print statements. When a program segfaults, does stdout not flush its buffer automatically? I don't understand why sometimes I need to use fflush() and sometimes not. Sometimes the stdio buffers are flushed sometimes they aren't. For example simply including a "\n" in the printed stuff will typically flush it (because stdout is by default line-buffered when attached to a terminal). When a program segfaults, does stdout not flush its buffer automatically

i have a long run server program(say, program A) which is written in QT/c++. the program is not so stable so i decide to write a python script to restart it if it crashes. the problem is that the program may started fail(if i gave it an in-use port), print the error and then just hang there without quitting, so i must monitor the stdout of the program and kill it on failed startup. this is a piece of my final code (well, in fact this is ok, you can just ignore it): self.subp = subprocess.Popen( r'.\A.exe -server %d' % portnum, stdout=subprocess.PIPE, bufsize=1) for line in iter(self.subp

Platform: windows 8.1 IDE: vs2013 use c/c++ Process A read stdout of subprocess using pipe redirect. but subprocess dont invoke fflush after printf, so processs A cant read anything from pipe before subprocess run to end. ps: I have souce code of subprecess, but its very hard to modify them. So whether Process A can force subprocess refresh stdout buffer to read something before subprocess run to end? (the same effective as fflush) 来源： https://stackoverflow.com/questions/22527010/how-fo-force-subprocess-to-refresh-stdout-buffer

I am using the following command to output IPs from live tcpdump capture sudo tcpdump -nn -q ip -l | awk '{print $3; fflush(stdout)}' >> ips.txt I get the following output 192.168.0.100.50771 192.168.0.100.50770 192.168.0.100.50759 Need 2 things: Extract only the IPs, not the ports. Generate a file with unique IPs, no duplicated, and sorted if posible. Thank you in advance To extract unique IPs from tcpdump you can use: awk '{ ip = gensub(/([0-9]+.[0-9]+.[0-9]+.[0-9]+).*/,"\\1","g",$3); if(!d[ip]) { print ip; d[ip]=1; fflush(stdout) } }' YOURFILE So your command to see unique IPs live would be