Shell Programming and Scripting

> sed ''
Hello
hi
Hello output
How
hi output
^D
How
>
sed should take each line as input, process and output the result. In the above scenario the input is passed from keyboard and the output of 'Hello' as you can see is displayed on the screen after 'hi' is passed as input but not as soon as we passed 'Hello'. Why?

sed provides a special address, $, which refers to the last line of the data. For this to work, sed must read ahead a line.

In this specific case, since that address is not used, it would be possible to immediately print a line, but that "optimization" would require a little more intelligence (complexity) for very little gain.

I'm curious. Do you have a reason to care about this? Is this behavior actually causing a problem? If so, demonstrate that and perhaps we can suggest an alternative.

Regards,
Alister