You've got Mail!

The mail command, unlike other commands we’ve taught you in this lab and previous ones, is especially unique: literally no one* uses this! As such, this section is not relevant to any course material. But the idea of sending each other mail via the terminal, all 1970s-core, is too appealing to pass up on.

*By "literally no one", I mean "literally no one, except for at least one person at this university", so I've been told.

Throughout this section, we’ll use myname and friendname to refer to your and your partner’s UCSD username, respectively. This is the username you use for your UCSD email, and the one you use to log into ieng6.

In order for mail to work, you and whoever you are mailing to must be on the same cluster on ieng6. You do not need to know what a cluster is, but you do need to know how to SSH into a specific one on ieng6. If each line of your command prompt starts with this:

[myname@ieng6-640]:~:500$

Then ieng6-640 is the cluster you are logged into. In order to SSH into a specific cluster, exit out of your current SSH session, and in your local machine terminal, type:

$ ssh myname@ieng6-640.ucsd.edu

And enter your password as usual. Make sure both you and your partner are on cluster 640.

In the following instructions, you will use the mail command, but it is not available on the ieng6-2xx servers. Please make sure to log out of ieng6 and then sign into ieng6-640.ucsd.edu! This specific cluster runs an older operating system that still has the mail command.

Once you and your partner are in the same cluster, try using the mail command to begin composing an e-mail (electronic mail). Either command below works:

$ mail friendname@ieng6-640.ucsd.edu
$ mail friendname@ieng6-640

This will prompt you with Subject: so you can type your email’s subject. The subject is only one line of test, so when you press Enter you are now typing the contents of your mail. When done writing your message, press Ctrl+D to finish and send.

Now, your partner can use the mail command by itself to see that they have received mail! It will have a number next to it as it enumerates messages every time you open the mail shell. Type this number and press Enter to see the message.

Now that you have mail and therefore can enter the mail shell, you can type ? to get a list of commands that you can use.

type <message list>          type messages
next                         goto and type next message
from <message list>          give head lines of messages
headers                      print out active message headers
delete <message list>        delete messages
undelete <message list>      undelete messages
save <message list> folder   append messages to folder and mark as saved
copy <message list> folder   append messages to folder without marking them
write <message list> file    append message texts to file, save attachments
preserve <message list>      keep incoming messages in mailbox even if saved
Reply <message list>         reply to message senders
reply <message list>         reply to message senders and all recipients
mail addresses               mail to specific recipients
file folder                  change to another folder
quit                         quit and apply changes to folder
xit                          quit and discard changes made to folder
!                            shell escape
cd <directory>               chdir to directory or home if none given
list                         list names of all available commands

A <message list> consists of integers, ranges of same, or other criteria
separated by spaces.  If omitted, Mail uses the last message typed.

Note that when the help dialog says "folder", this is a bit of a misnomer. The "folder" is actually the filename that the command will use. For the save and copy commands, you can give it a valid path to a file and it will save or copy the contents of the email into the file. The path is relative to wherever you opened the mail shell.

You will likely not need to use all of these commands but at least a few are worth noting:

• type <message list> can be used to print out the contents of selected messages. For example, type 3 4 prints out the contents of messages 3 and 4.
• headers will print out the list of enumerated messages along with their senders, subjects, and statuses.
• You can respond to a message with Reply <message list>, which will open a response to the message to type in a reply. Again, you can finish and send with Ctrl+D. For example, Reply 5 opens a response to message 5.

There also exists another method to send mail from outside the mail shell, using the pipe operator we learned earlier. This command also makes use of the echo command, which outputs its argument to stdout. Sounds redundant, but it’s intended to be used in this way to input strings into other commands, or to be used as print statements in bash scripts.

$ echo "email body here" | mail -s "subject here" friendname@ieng6-640.ucsd.edu

Trading Pokemon

We can also use email to send attachments in the form of files. In this section, we’ll trade Pokemon with each other via mail. We will use the pokeget.sh script provided in your lab starter code for fun to generate some files with Pokemon in them. First, let one person be the sender, and the other will be the receiver. After you can successfully send and receive Pokemon from one to the other, swap roles and try sending one the other way.

Sender

Use the below command to generate a ".pk" file with the name of the Pokemon you picked. For example, if you picked Pikachu, #25, you would call this file pikachu.pk. Alternatively, if you want the receiver to not know what the Pokemon is until they open the file, you can call it mystery.pk. Feel free to replace 25 with the National Dex number of any Pokemon.

./pokeget.sh 25 > pikachu.pk

If the pokeget.sh script seems to take more than a few seconds to finish running, try using Ctrl + C to interrupt the program and try running the same command again.

Once you have a ".pk" file, use the following command to send it to your partner, using the -a option. Replace "pikachu.pk" with the name of your Pokemon file if it is different.

$ echo "email body here" | mail -s "subject here" -a pikachu.pk friendname@ieng6-640.ucsd.edu

Receiver

Open up your mail shell with the mail command. You should have a new email if the sender did their job properly. Type the following command to save the email you received as a file, with n replaced by the ID number of the email. Note that the "&" is the prompt, and does not need to be typed, just like "$" in the terminal.

& save n pokemon.mail

Extracting the attachment in a readable form from the email itself is quite involved, so please use the provided script to get your Pokemon:

./extract_pokemon.sh pokemon.mail > pokemon.pk
cat pokemon.pk

If you get an error running extract_pokemon.sh that mentions something about a bad interpreter, this is likely because the file hasn't been formatted for unix correctly yet. Run sed -i 's/\r$//' extract_pokemon.sh to reformat the file and try again.

If everything went well, you should get the Pokemon your partner sent you! Have a bit of fun with this and send each other some cool Pokemon.

Adding Pokemon to .bash_profile

If you would like your Pokemon to appear when you open ieng6, you may do the following.

If you would like 1 Pokemon, add the line cat ./path/to/pokemon.pk (replace the path with the entire path to your Pokemon file, starting with ~) to the end of the .bash_profile file in your home directory.

If you would like 2 Pokemon, add the line paste ./path/to/pokemon/bigPoke.pk ./path/to/pokemon/smallPoke.pk (replace the path with the actual path to your Pokemon file) to the end of the .bash_profile file in your home directory. Note that if you paste the smaller Pokemon first, the larger one will be cut in half. You are welcome to try to troubleshoot this.

If you want to do the same thing on your own computer, you can add this same line to your .bash_profile or .bashrc file. Just make sure to download the referenced .pk files using pokeget.sh and edit the paths as needed!