Function keys can be interpreted by the window manager or terminal emulator (you'll find that F11, for example, will usually maximize the window) or passed through to the program as VTxxx or ANSI escape sequences. 

F9 on Linux and Solaris usually sends ESC[20~. Depending on the versions of the software, bash or ksh will interpret this as either 0~ or ~. On the other hand, if your shell is dash, which doesn't do any line editing, you'll see ^[[20~.

To make F9 send ~:

If you're using X (tested on a US layout keyboard):

xmodmap -e "keycode 75 = asciitilde"


On a Linux console, run showkey to find F9's keycode. On my system, it's 67.
Then run this (you may need to be root):

echo "keycode 67 = asciitilde" | loadkeys


On a Solaris 10 console, run showkeys | more to find F9's keytable entry. On my virtual machine with virtual USB keyboard, it's key 66 all tf(9). Then create a file with these contents:

key 66 all ~


and run loadkeys /path/to/file.

Tilde on unix:hpux and / or solaris
I have a windows server and I set my domain name servers to this server. now I want send email from another server, really my web application and mail server aren't on a same server. the mail server is Linux CentOS. and there are many mail accounts available on it. so it has no problem. now I want to to send and receive emails from the linux server and my website be on the windows server. so I changed MX record of my domain to Linux server. but when I send mail from the mail server to gmail.com it's response is:

 Client host rejected: cannot find your reverse hostname


what is wrong? I searched for this problem but I couldn't solve this problem. I want to ask you what is the steps to change mail server? did I forget some Steps?
