Re: tail and grep
On Tue, 7 Jul 1998, Patrick Olson wrote:
> when I try tail -f /var/log/messages | grep "local IP"
>
> it prints (with a real IP address instead of 123.123.123.123)
>
> Jul 7 20:06:00 server2 pppd[587]: local IP address 123.123.123.123
>
> on my console. That's exactly what it should do. But if I try to
> redirect it to a user's file (so he can see what his dynamic IP is) using
>
> tail -f /var/log/messages | grep "local IP" > /home/pppusers/dynamic.IP
>
> it does nothing but create a 0 byte file.
>
> Questions:
>
> 1. What am I doing wrong?
The reason the redirection doesn't work as expected is that "tail -f" doesn't
send EOF, so although /home/pppusers/dynamic.IP gets opened the buffer doesn't
get flushed, so the file doesn't get written to.
Cheers,
Ted.
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E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk>
Date: 08-Jul-98 Time: 12:31:15
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