Misc. Linux bash questions

(1) OK, let's say I'm looking for the file "hostid". As a normal user, I know that "hostid" must reside in one of the $PATH directories.

How do I pipe the output of "echo $PATH" into "find" to get Linux to only search $PATH directories?

(2) Is it possible to pbutt variables around in scripts? For example, consider the simple script below:

cp -rftmp-xyzhome-work-xyz

How do I replace set "-home-work-xyz" to the output of pwd so that the script automatically copies the contents of "-tmp-xyz" to the current directory without having to modify the script each time?

(3) How do I recursively compare files either with md5sum or diff?

E.g. Let's say the main "nohup.out" resides inhome-work-1 Other "nohup.out" reside inhome-work-1-1....M

I want to check the differences in the main one with the sub-ones. Why does my attempt at this below not work?

home-work-1

(4) How do I check if a CPU is free using some kind of remote no-interactive-pbuttword ssh in realtime (so no periodic polling)? I will Google for the latter as "ssh no pbuttword", but I am not sure what to look for for the former.

One way I thought of was to poll for an output file periodically, but this is inefficient.

(5) How do you use grep to output ranges of values or only search in specific columns?

19452 me 25 0 84852 25m 4564 R 99.9 2.5 1:47.81 mersenne 1 root 16 0 688 260 224 S 0.0 0.0 0:01.39 init 2 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd-0 3 root 10 -5 0 0 0 S 0.0 0.0 0:00.22 events-0 4 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 khelper

The above is the first few lines of "top". I would like grep to look in the CPU% column for all values from 50.0 - 120.0

Thanks for any buttistance.