A few questions about Linux commands?

No. The fist 2 do. The third one takes you to the root home folder but you would need to be root to do this.

Appending anything to a file requires a pipe command :

cat "abcdefg" file.log <<

every one of those but cd ../../root (1,2,and 4) are the same thing

I should note if you change $HOME then they all don't work (besides number 3)

cd ../../root goes two directories up and into a root folder if one exists. It depends what your current working directory is ... this is called a relative path (because its relative you your current working directory)

if my home directory is /home/jeff and my current directory is ~/bin/coolness/ then doing cd ../../root will put me at /home/jeff/root/ which is not the same as the other commands obviously

./script.sh >> poop.log

edit: you must have >>

file.sh >> file.log

cd ~ This is valid in C Shell only. However, today bash is mixture of C and bourn shells. Thus, it will work.

cd ../../root This takes you root directory which grand parent to your current directory.

If you are currently in /home/root then it takes to /root directory is it is existing

cd this command takes to our home directory. Rather users home directory.

Main difference is who is executing the command. If the super user root is working then all the above may be same. Else not