When sed is redirected to a file, it buffers it's output.
So, unless you waited for the script to execute long enough
(almost 6 minutes by my estimates) to fill the stdout buffer
at least once, you won't see anything.
However if you do the same thing without the 2 sec delay e.g.
while :; do echo hello; echo; done | sed '/^$/d' > /tmp/f
you will notice that /tmp/f fills quite rapidly.
Doug.
Aubrey Li wrote:
Hi list,
A silly question here:
A simple list I wrote to test
=====================
$ cat test
#!/usr/bin/sh
#
while true;
do
echo hello
echo ""
sleep 2
done
=====================
if I run it as the following:
$ ./test > tmp.txt
of course I can get something from tmp.txt file
And if I run it as
[aubrey-...@~]./test | sed '/^$/d'
hello
hello
hello
Blank line will be filtered by sed, but if I run it as
[aubrey-...@~]./test | sed '/^$/d' > tmp.txt
Nothing is in the tmp.txt.
What's wrong I did?
Thanks,
-Aubrey
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