How to find the exit code of last shell command?
In bash, echo $? prints the exit code of last command.
when you type kill in terminal, is it calling bash builtin or /bin/kill?
If you are using bash, type type kill to find out.
In Ubuntu 12.04, clearly it's calling the bash version. You can confirm by comparing the output of:
kill -l /bin/kill -l
How do i start bash without loading any init files?
start bash by bash --noprofile --norc.
See also: What's the Difference Between .bashrc, .profile, .bash_profile, …?.
How to do set font for xterm?
In xterm, hold 【Ctrl】 then right click to change font size. Also, Left and middle click change other options.