Re: OT: tail -f | while read

[miquels@cistron-office.nl (Miquel van Smoorenburg)]

In article <[🔎] 20010906132309.A4847@fishbowl.madduck.net>,
Martin F Krafft  <madduck@madduck.net> wrote:
>hi,
>why does the following not work:
>
>  tail -f /var/log/syslog | grep something | while read i; do myprog $i; done

It's because grep uses stdio, and it buffers the output at some
blocksize (1K / 4K / 16K or something) before it outputs anything
if the output is not a terminal .. not much you can do about it.

A solution would be:

tail -f /var/log/syslog |
	while read i; do grep -q something "$i" && myprog "$i"; done

Or, more efficiently,

tail -f /var/log/syslog |
	while read i
	do
		case "$i" in
			*something*)
				myprog "$i"
				;;
		esac
	done

Mike.
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