Description
Before starting this lab exercise, pay attention to the presentation by the lab instructor on starting
X11 (XWindows) via XQuartz, starting an xterm, accessing tuxworld via ssh in that xterm window, and
then running an XWindows client on tuxworld. Follow along on your workstation with the lab instructor,
replicating what he does, and make sure that you end up with the same results.
Perform each of the tasks below in a virtual terminal window. For each task, copy-and-paste the contents
of your virtual terminal window (including the commands that you typed, as well as any output produced by
the commands you gave) into a text file called lab2.txt. However, do not include extraneous or superfluous
commands or output; only include content relevant and essential to the specified task. Then, with a text editor, add text and identifying information to clearly distinguish which commands/output/code
correspond to each task. Submit lab2.txt through moodle when done. The submission is due at 11:55
p.m. on Thursday, September 22. This lab is out of a total of 14 marks, with each question (1a, 1b, . . . ,
3e) being worth one mark except for 2(d) which is worth 2 marks. Unless otherwise specified, all commands
should be run on tuxworld using the bash shell.
1. (a) Create a directory called 214lab2 under your home directory, and then cd to it. Use this new
(sub)directory as your current working directory when completing all the remaining tasks in this
lab.
Use the touch command to create 15 (empty) files called file1.txt, file2.txt, . . . , file14.txt,
file15.txt. Also use touch to create five files called data1.dat, . . . , data5.dat.
The touch command is described on pages 985-986 of the Sobell text. Note that you can give
multiple arguments to a single touch command.
You may also be able save some typing by using “arrow keys” on your keyboard. With the “up
arrow” key you can retrieve the last input line, and with the “right arrow” and “left arrow” keys
you can position your cursor within the retrieved line so that you can make local edits to it.
When you have completed your local edits, typing the “return” or “enter” key will cause bash to
interpret your edited (input) line. Page 31 of the Sobell text gives more information.
(b) Use a UNIX command involving filename wildcards to list all the files in your 214lab2 directory
(from step 1a) that end in “.dat”.
(c) Use a UNIX command involving filename wildcards to show the permissions, owner, group, etc.
for (only) the files file10.txt, . . . , file15.txt (in your 214lab2 directory from step 1a).
(d) Invoke the file(1) command on (only) the files file1.txt, file3.txt, file4.txt, file6.txt,
and file9.txt. Use a single command involving filename wildcards to do this.
If you need supplementary resource material on use of filename wildcards beyond what was given in
class, you may find pages 148-152 in the Sobell text useful.
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2. (a) Use a UNIX command to (try to) delete the file fake_file.txt in your current working directory
(214lab2 from step 1a). Do this step even though fake_file.txt does not exist. Your command
must be structured such that, if the file exists, you are not prompted for confirmation, and if the
file does not exist, no error message is printed. Consult the appropriate manual page to learn how
to do this; i.e. consult a relevant man page or info page for the options you need.
Submit your command and any output generated. Do not submit any logs from consulting man
page or info pages.
(b) Use a text editor or UNIX command to create a file called my_name.txt that contains your name
and student number. (Log of using the editor does not have to appear in your lab2.txt.) Use
a UNIX command to concatenate the contents of my_name.txt and fake_file.txt (which, as
a result of the previous question, does not exist) and output the result to the default standard
output.
Note that an error message regarding the nonexistence of fake_file.txt should be produced.
(c) Repeat the above command (step 2b), except redirect standard output to the file standard_output.txt
and redirect standard error to the file standard_error.txt. Then show (i.e. output to the terminal) the contents of standard_output.txt and standard_error.txt.
(d) Remove files standard_output.txt and standard_error.txt. Then execute the same command as in part 2c, except discard any output sent to standard error. In other words, the error
output should not be printed to the screen or output to a file on disk, but rather redirected
in such a way that it is discarded. Then show (i.e. output to the terminal) the contents of
standard_output.txt. Finally, with an ls command, demonstrate that standard_error.txt
does not exist (was not created by your command).
If you need supplementary resource material on redirection beyond what was given in class, you can
consult pages 133-141 and 282-284, among others, in the Sobell text.
3. (a) Run the program (command) top. Then suspend this process.
(b) Run either the env or printenv command, and in the output identify (visually) the environment
variable that contains the current user name. In lab2.txt you only need to have the output from
the env or printenv command for this step.
(c) Look at the manual page for pstree (with either the man or info commands) to find the option
which will direct the command to display the PID of each running process. Give this option to
pstree. In addition, provide as an argument to the command the expansion of the environment
variable you identified in step (b). The result should be a hierarchical view of all your processes
complete with PIDs. Locate the PID of the top process you started (and then suspended) in part
(a). In lab2.txt show the pstree command you used and the output from that command.
(d) Use a UNIX command to send signal 9 (SIGKILL) to your suspended top process. Obtain the
necessary PID from the output in question 3c. After entering your command, type an extra
“return” (or “enter” on some keyboards) character to the shell. You should get a message telling
you that the top process has been killed.
(e) Repeat the pstree command from step 3c and confirm that the top process is no longer running.
In lab2.txt again show the pstree command you used and its output.
The Sobell textbook has useful information on all the commands used in Question 3.
