M.I.T. DEPARTMENT OF EECS
| 6.033 - Computer System Engineering | UNIX Hands-On Assignment |
Complete the following hands-on assignment. Do the activities described, and submit your solutions via Gradescope by 11:59pm on 2/21. This assignment is longer than the DNS one.
Before attempting this hands-on, you should read The Unix Time-Sharing System, which is also assigned for this recitation. You might also find Section 2.5 of the book useful for questions 8-19.
Log into an Athena machine (athena.dialup.mit.edu is
ok) and get access to the Athena command prompt. If you logged into
an Athena dialup machine, you should see the prompt in your ssh
client. If you logged into an Athena workstation you may need to open
a terminal window. The prompt should look something like this (the
"no-knife" part may say something different):
no-knife:~>
Use the add command to gain access to the 6.033 utilities you will use in this assignment.
no-knife:~> add 6.033
Some of the directions in this hands-on assume your UNIX shell is tcsh. Run the following command to ensure you're running the appropriate shell. After you run tcsh -f your prompt will change to a single >.
no-knife:~> tcsh -f
We'll start off with an extremely simple example that most of you are probably familiar with already:
> cd /bin
> ls -1 | more
Here, we are first changing into the /bin directory, which contains
many of the executable commands for the system. The command ls
-1 gives us a listing of all the files in the current directory
with one file per line. (Note that -1 is the numeral
"one", not the letter "L".) We then pipe the output from
ls to the command more, which displays the
results one page at a time. (Press the space bar to show the next
page. In order to quit the enumeration, press q.) You can refer to the
manual pages for ls and more to see more details
and options for each command. Manual pages let you read information about
various commands on UNIX systems; to use them, run
> man command
where command is the command you are interested
in. If you are unfamiliar with manual pages, you may want to try
running
> man man
for information on the man command itself. Keep in mind that the
manual pages for basic commands vary from system to system (much as
the commands themselves do).
Now, try this:
> cd /bin
> ls -1 | grep p | more
This runs the same ls -1 command, but only lists the
executable files which happen to contain the letter "p" somewhere in
their names.
The point here is to observe that you can chain together multiple commands using the pipe character ( | ), and the output from each command will be passed to the input of the next, in left-to-right order. This allows you to treat any command that uses standard input and output as a primitive from which you can build more complex and useful commands.
Now, we'd like you to figure out on your own how to solve some problems by chaining different commands together.
If you aren't already familiar with these commands, you may want to briefly skim through their man pages to familiarize yourself with what they do. You will probably need to use some of the options for the different commands in order to solve these problems.
Here are the commands you may find useful:
cat fmt grep head ls ps sort tail top wc yes (*)
(*) On some Athena machines, the yes command isn't
available. However, if you are doing this assignment on Athena you
can use the command gyes, which is functionally
equivalent. gyes is located in the "gnu" locker, so
before you can use it you need to add the locker. You can do so with
the following command:
> add gnu
(If you are curious about Athena's locker system, you can run
man lockers for more information. The command
whichlocker can be used to determine which locker
contains a given command. The whichlocker command itself
resides in the "outland" locker. For more info on other lockers, look at
this SIPB article)
Once you have added the gnu locker, you can use gyes
instead of yes. Some Athena machines seem to lack the
manual pages for both yes and gyes
(hereafter referred to just as yes). In case the man
pages are missing on the machine you are using, here is a brief
description of what yes does. yes is very
simple; it just outputs a string repeatedly until killed. It takes
either one or zero arguments; if you give it a string as an argument
it will output that string until it is killed (you can kill a process by
pressing control-c). If you give it no
arguments, it will output the string "y" until it is killed, which
explains why it is named yes.
Now you're ready for this week's questions.
Like before, the questions are in a read only google doc. Make sure to enter quesitons in the page indicated and upload them as a PDF to Gradescope. See more detailed instructions at the end of last week's hands-on. If you are having Gradescope questions, please post a question on Piazza!
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