egrep doesn't stream output if not to tty

[Tilman J. Rothe]

Subject: egrep doesn't stream output if not to tty

Hi,

egrep writes its output only after the input file has closed if output
is redirected:

: 0 13:43 address@hidden:~;  egrep -v -e 'some (.*) \1' 2>&1 #|cat
after this line, egrep echos output immediately
after this line, egrep echos output immediately
so the next line is read after some output has been done.
so the next line is read after some output has been done.

: 0 13:46 address@hidden:~;  egrep -v -e 'some (.*) \1' 2>&1 |cat
Now after this line I'll wait a full minute after cpu usage has gone to zero
but egrep writes its output only after I pressed C-d at the end of this line.
Now after this line I'll wait a full minute after cpu usage has gone to zero
but egrep writes its output only after I pressed C-d at the end of this line.

: 0 13:38 address@hidden:~; egrep --version
egrep (GNU grep) 2.4
: 0 13:49 address@hidden:~; uname -a ; cat /etc/SuSE-release 
Linux Rechner 2.4.0-test10 #8 Mon Feb 12 12:39:18 MET 2001 i686 unknown
SuSE Linux 6.4 (i386)
VERSION = 6.4


It also "works" the same way if input is redirected, too. If this
behavior is somehow intended for performance reasons, please make a
switch to turn it off. I'm trying to do : (This should print all
unusual syslog messages onto the X root window)

egrep -v -f trivial_messages </root/fifo_from_syslog >tempfile &
root-tail tempfile &

Have a nice day,
Tilman J. Rothe <address@hidden>