http://www.pixelbeat.org/programming/stdio_buffering/
----- Original Message ----- > Isn't there a way to tell bash not to buffer an output descriptor? I > know you can do it with ioctl inside C/C++. > > -----Original Message----- > From: [email protected] [mailto:[email protected]] > On Behalf Of Steven S. Critchfield > Sent: Wednesday, February 19, 2014 12:02 PM > To: [email protected] > Subject: Re: [nlug] Weird CentOS 6 Bash/Grep issue > > ----- Original Message ----- > > OK, the mystery shifts. If I don't setup the "real time" (sub-level > > child?) > > with the '-f' and just do a same level operation such as: > > > > tail -500 /var/log/pfsense | egrep -e '\.25\:' -e '\.465\:' -e > > '\.587\:' | grep -v '192\.168\.0\.71' > > > > it works as desired! > > > > Something with the child process of the tail that is continuously > > reading the target(s) and feeding them to STDOUT in real time > > doesn't like that fork to the 2nd grep. I tried encapsulating the > > tail in '(' > > and ')' but no go. > > What you are seeing is really simple. It is output buffering. Since > the tail > above sends out a block and then EOF, the first grep can filter and > EOF, then the final grep can filter and EOF flush. > > In the other, you are waiting for a buffer fill before it will start > displaying. > > -- Steven Critchfield [email protected] > > -- > -- You received this message because you are subscribed to the Google > Groups "NLUG" group. > To post to this group, send email to [email protected] To > unsubscribe from this group, send email to > [email protected] For more options, visit this > group at > http://groups.google.com/group/nlug-talk?hl=en > > --- You received this message because you are subscribed to the Google > Groups "NLUG" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > -- > -- You received this message because you are subscribed to the Google > Groups "NLUG" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] For more options, visit this > group at http://groups.google.com/group/nlug-talk?hl=en > > --- You received this message because you are subscribed to the Google > Groups "NLUG" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. -- Steven Critchfield [email protected] -- -- You received this message because you are subscribed to the Google Groups "NLUG" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nlug-talk?hl=en --- You received this message because you are subscribed to the Google Groups "NLUG" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
