As you go through the exercises today, reference the following for help
along with these more obvious sources of information (in no particular order):
- the MacLab's online
man pages for details on specific commands, and
- the vi and emacs tutorials and cheat-sheets
linked from Ken Harris's
- the web,
- the TA, and
- your classmates.
The sections below contain short exercises intended to familiarize you
with working in a Unix environment. Your goal is to refresh the Unix
know-how you gained in CMSC 152/162, and maybe pick up some new tricks.
Create a document (plain-text,
PDF, or Postscript) containing your solutions, using either the
vi or emacs editor, and email it
with subject line CMSC 15400: Lab 1, by 5:00pm.
Files and Directories
As you follow the directions below, copy the shell command(s) which
accomplish(es) each bulleted task (but not the output) into your
- Within your home directory, create a directory for your
work in this course, using the mkdir program.
Choose an appropriate name, such as cs154.
- Create a subdirectory for today's lab.
Choose an appropriate name, such as lab1. cd
to this directory.
- List the contents of the directory
~clklein/html/15400-2008-spring/lab1/ by size,
using the program ls.
- Use find to locate all .tar and
.tar.gz files within that directory. Next, copy them to the
subdirectory you created for this lab.
- Extract the files from these archives using tar and/or
- With a single command, delete all
files with extension .del from the extracted directories.
Hint: first use the
find command to identify them. Next, extend this command by
applying the -execdir (or -exec) flag, which runs the specified program
on each file it finds. (See the EXAMPLES section of
find(1), the find man page, if you have trouble with the
- Make a directory named tmp in the directory you created
for this lab. Copy all .sh files
from the root of either extracted directory to this tmp
- Execute one such .sh file, rename it (to anything), change its
permissions so any user can write to it, and finally delete it.
- Create a copy of the (entire) tmp directory then delete
- Archive either extracted directory, creating the tarfile
mytar.tar then compress it using gzip.
Alternatively, create a compressed tarfile directly with a single
tar command by also including the -z flag.
Processes, Pipes, and Redirection
Again, copy the commands which accomplish these tasks to your
- Use head and tail to view the first and last
eleven lines of a file.
- Pipes, a mechanism for interprocess communication, can be used to
feed the output of one program into another program. For example, the
command history | grep chmod feeds the output of the
history command to grep, which here searches for uses of
chmod. Use a pipe, head, and tail to read
the first five of the last ten lines of a file.
Direct a command's output to a file, rather than to the terminal or
to another process, by appending > $filename to the
command (replace $filename with the path of the file that
should collect the output).
- bc is an interactive calculator, which by default reads
its input from the terminal. Instruct bc to read instead from
the file ~clklein/html/15400-2008-spring/lab1/bc_input
by appending the token < then that path to the command that invokes
- Many common C header files reside in the directory
/usr/include/ and its descendent directories.
With a single command, produce a file containing all the #include
lines that appear in the header files in or below
/usr/include/sys/. The lines of this file should be
sorted and have no duplicates. Hints:
- Use find to identify these header files.
- The command grep ^\#include /usr/include/stdio.h outputs the lines of
interest for stdio.h.
- Use sort and uniq.
- Start a long-running command (e.g., top),
suspend its execution with control-z, resume its
execution with the command fg, and finally terminate the process
with control-c. (Don't bother include this in your solutions
- The program sleep does nothing for the specified number
of seconds before terminating. Execute sleep in your session's
background by appending & to the command. Note
that you may enter new commands while some others execute in the
- Execute sleep 1000 &, noting the process id assigned
to the background process. Execute kill $pid to kill
this background process.
ssh to your neighbor's machine. Pipe the output of ps
aux to grep to check that your neighbor is not running
To execute shell commands sequentially, separate them with a
semicolon, e.g., do_one_thing; then_another. To execute the
second command only if the first
instead separate them with the
token &&, e.g., mkdir foo && rmdir foo.
Write a single shell command to download, compile, and execute
this program, deleting the executable created when it finishes. Hints:
- Use wget -q -O - to download the program and write it to
- Instruct gcc to read from standard input using the flags
-x c -.
- Use a pipe to communicate between these processes.
- Don't forget to set the executable bit on the binary gcc
- Environment variables are one way in which Unix programs
read configuration options. The shell built-in set displays
the current environment configuration. Example environment variables
include PATH, the search path for commands, and
PRINTER which specifies the default printer for many programs.
Extend your PATH variable to include the current working directory
(identified by the dot character) using the export command:
export PATH=$PATH:.. Show that with this extended path it's
not necessary to prefix programs in the current directory with ./ to
execute them. (Don't bother including this in your solutions file.)
a Sed and Awk Micro-Primer
This lab's original incarnation was inspired by
CSE 303 course website.