UNIX for Dummies Questions & Answers

20 is the ASCII Hexadecimal for the Space character. What software wrote this file? If it was Microsoft HTML it would be %20 not #20 .
What software are you using to view this file?

Can you post a definitive view of a couple of records with the unix od command (preferably with output in hexadecimal)? Command syntax varies according to your Operating System (not posted). Use man od .

I think what is happening is that the sed that is printing matching records knows that stdout isn't a tty and is buffering the output. The number of records that match and are printed aren't enough to fill and flush the buffer, so it appears as nothing is being output from the second sed. By reversing the sed commands, the volume through the first was large enough to flush the buffer and the output from the second sed isn't buffered because stdout is the tty.

This is probably very close to what you tried that worked, just a wee bit better because there is only one sed process:

Code:

tail -f log-file | sed -n "s/#20//g; /$*/p"

Not as efficient as the replacement is done to records that aren't printed, but stdout of the sed is a tty and output shouldn't be buffered.