CMPS-012M Lab 1 • Hello World in Java ; gmake ; RCS

Description

1. Overview
This lab will introduce you to Unix if you are not already familiar with it, and show you how to compile and execute a Java program. It also helps you with a first pass at understanding : AFS, the file
system where your files are kept, and access control lists ; RCS, the revision control system, which
helps you keep backup copies of all of your work ; gmake, which helps you with building executables
from source code ; and automatically setting the $PATH variable by means of dot files in your home
directory.
2. Directories and ACLs
Change directory to your home directory and create a subdirectory called private. Then make a subdirectory of that called cmps012m, and a subdirectory of that called lab1. In the following, bolface is
what you type, and plain face is what is typed at you :
bash-1$ cd
bash-2$ mkdir private
Make sure you protect the directory against other users :
bash-3$ fs setacl private $USER all -clear
bash-4$ fs listacl private
Access list for private is
Normal rights :
foobar rlidwka
At this point, there should be only one ACL on your private directory, namely your own, where foobar is shown above should be shown your own username. The shell variable $USER is your own username. You may wish to type it in explicitly instead. If there are any other ACLs on your private
directory, you must delete them. Note that you may also lock your home directory to all ACLs but
your own. That means, however, that you may not have a web page.
You must understand ACLs in order to protect your files. Some special ACL usernames are : wwwadmin is the IC web server, which needs read permission on your directory public_html, if you have one,
and list permission on your home directory. system:authuser is anybody with a IC account. system:
anyuser is anybody anywhere in the world on any machine running AFS. Try ls /afs.
You should have a separate directory for each course and each assignment. So create a directory
using the following :
bash-5$ cd $HOME/private
bash-6$ mkdir -p cmps012b/lab1
bash-7$ cd cmps012b/lab1
The shell variable $HOME may also be replaced by a tilde (~) as the name of your home directory.
When you use cd without an operand, it sets the current directory to your home directory. You may
wish to use two separate course directories, one for your CMPS-012B work, and one for your
CMPS-012M work, or you might want to use just one. You may, of course, call them anything you
like. In order to organize your files, make a separate subdirectory for each course, and under that, a
subdirectory for each project in each course.
3. Hello.java
Now begin work on lab 1. Create a file called hello.java, as shown in Figure 2 (page 6). It is a
slightly more complicated version of the standard ‘‘Hello World’’ program used to introduce programming languages.
If you use the command ls -la in my directory, you might notice a subdirectory containing that code.
If you like, you may copy it into your lab directory instead of copying it in. Files beginning with a dot
CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 2 of 10
are not listed with ls(1) unless the -a flag is given.
4. RCS
Although not required in future assignments, it is a good idea to keep many backup copies of your
work. RCS is a good utility to keep track of backup copies. Doing backups is like voting in Chicago :
Do it early ; do it often. If you don’t have backups, you will have to depend on the IT department to
recover yesterday’s copy. Murphy’s law says that the most important changes won’t be in that copy.
The corollary also says that you will lose your files so close to the due date that IC won’t get your
backups back to you in time. In this case, you will get a 0 on the assignment for not submitting anything.
Note that the code above has a magic string in it: $Id$ . These track your development progress.
For the initial checkin, do the following :
bash-8$ mkdir RCS
bash-9$ ci -zLT -s- -t- -m- -u hello.java
RCS/hello.java,v <-- hello.java initial revision: 1.1 done Now you have your initial version. Look at the man page for ci for all of the options. You will also want to read the co page. The options were : -zLT causes the time stamp to be in local time instead of UTC, -s- sets the state to −, -t- suppresses the descriptive text, -m- suppresses the log message, and -u checks in the file unlocked, thus not destroying the source. Unfortunately, the file is now read-only, so you may want to make locking non-strict : bash-10$ rcs -U hello.java RCS file: RCS/hello.java,v done bash-11$ chmod u+w hello.java bash-12$ ls -la hello.java -rw-r--r-- 1 foobar user 465 Sep 14 18:42 hello.java Oops, you forgot to put your name and username at the top of the file. Edit the comment on the first line to reflect your name and username. Every file you submit must have a comment on the first line with your name and username in it. Add in your name and username. Now check in another copy to make a backup. bash-13$ ci -zLT -s- -t- -m- -u hello.java RCS/hello.java,v <-- hello.java new revision: 1.2; previous revision: 1.1 done Use cat to look at the new version of your file. There are some alternatives to RCS : SCCS (very old). CVS (more flexible but more complicated). SVN (some people like using this). There are also some others. 5. The $PATH variable There are some commands given in this lab which are not generally available Unix commands. These are cid and checksource. You will notice that you get an error message when you use them : bash-14$ cid hello.java bash: cid: command not found This is because they are not in your path. These commands, among many others, are in the directory /afs/cats.ucsc.edu/courses/cmps012b-wm/bin/. You should add this directory to your path. How this is done depends on which shell you are using. The file /etc/shells lists all of the ones available : /bin/bash, /bin/csh, /bin/ksh, /bin/mksh, /bin/sh, /bin/tcsh, /bin/zsh. We will discuss only tcsh and bash in this document and ignore the others. Since we are using Linux, /bin/sh does CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 3 of 10 not exist, and is a symbolic link to /bin/bash. Also, /bin/csh does not exist, and is a symbolic link to /bin/tcsh. To find out which shell is your default, use the command : echo $SHELL Create or modify three files : ~/.cshrc, ~/.bashrc, and ~/.bash_profile. Modify your path for both shells as follows : (a) For tcsh, add the following line to the end of your ~/.cshrc file : set path=($path /afs/cats.ucsc.edu/courses/cmps012b-wm/bin) Then source it with the command : source ~/.cshrc For this command to work, you must be interacting with tcsh. (b) For bash, add the following line to the end of your ~/.bashrc file : export PATH=$PATH:/afs/cats.ucsc.edu/courses/cmps012b-wm/bin Then source it with the command : source ~/.bashrc For this command to work, you must be interacting with bash. If your current shell is tcsh, type the command bash before running the above command. Since bash differentiates between a login shell and a subshell, You should also have the file ~/.bash_profile source ~/.bashrc. This is done by putting the following line in your ~/.bash_ profile file : source ~/.bashrc The sourcing command does not need to be typed in every time you log in. Shells source their start files automatically. Any command or alias you want executed automatically every time you log in should be placed in the appropriate startup file. The last two letters, ‘‘rc’’ mean ‘‘run commands’’. If your shell is currently tcsh and you want to use bash, just use the command bash at the prompt. Or follow the instructions printed by the command chsh if you want to make this permanent. When you log in using tcsh, the file ~/.cshrc is automatically sourced, followed by ~/.login, which you probably may ignore. When you start bash by typing in the command at the command line, the file ~/.bashrc is automatically sourced. But if bash is your login shell, then at login, ~/.bash_profile is automatically sourced. Submit your files .cshrc, .bashrc, and .bash_profile, using the command : submit cmps012b-wm.f13 lab1 .cshrc .bashrc .bash_profile This command must be done in your home directory. 6. The script checksource Use the script checksource to check on some basic formatting items. Edit your files so that it does not complain. If you run checksource without filename operands, it will print out a text-format manual page. To check up on hello.java, use the command : bash-15$ checksource hello.java 7. The script cid An alternative to using ci directly is the program cid, to be found in various locations in this directory structure. See the comments at the beginning for details. It works just like ci, but automatically creates the RCS subdirectory and does the correct locking. To fetch backadeleted file, use the co command. You will find that the cid command is much simpler to use, since it automatically sets up the RCS subdirectory and appropriate file locking. In order to find where that script is, you can do the following : bash-16$ cd /afs/cats.ucsc.edu/courses/cmps012b-wm bash-17$ find * -name cid -follow 2>/dev/null
This says find all files whose name is cid, even if you have to follow symbolic links. Without the
CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 4 of 10
redirection 2>/dev/null, you will get lots of error messages because of directories that you don’t have
permission to access. With this redirection, error messages will be sent to /dev/null, the bit bucket.
Try it both ways, with and without redirecting stderr. This works if you use bash or sh as your shell,
If you use csh, you should instead use
csh-% sh -c ’find * -name cid -follow 2>/dev/null’
which will pass the command to the Bourne shell to have it executed. There are many small differences between the shells. Inside of a Makefile, always use Bourne shell syntax, and never use the
born-again shell syntax or csh syntax. Read http://www.faqs.org/faqs/unix-faq/shell/. You may
find something of interest in http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/.
8. Running the program
The output of running the program is shown in Figure 1. The figure was actually generated from the
gmake process that created this document. A Unix pipe was used. If you don’t want to type in the
entire ‘‘hello’’ program, you may copy it from the hidden (or ‘‘dot’’) subdirectory. This directory will
not show up if you are using a browser. Log into unix.ucsc.edu and find it with ls -la.
1 %%%%%%%% hello
2 Hello, World!
3 Class path is
4 /afs/cats.ucsc.edu/courses/cmps012b-wm/Labs-cmps012m/lab1u-gmake-rcs/.files/hello
5 Operating system is 64-bit little-endian amd64 Linux 2.6.32-358.18.1.el6.x86_64
6 Runtime is Java(TM) SE Runtime Environment (1.7.0_25-b15)
7 Virtual machine is Java HotSpot(TM) 64-Bit Server VM (23.25-b01)
8 Home is /usr/java/jdk1.7.0_25/jre (1.7.0_25)
9 There are 59529984 bytes = 58134.75 Kbytes = 56.7722 Mbytes of free memory
10 Time is now 1380244101.005 seconds = Thu Sep 26 18:08:21 PDT 2013
11 %%%%%%%% Exit status = 0
12 %%%%%%%% uname -a
13 Linux unix1.lt.ucsc.edu 2.6.32-358.18.1.el6.x86_64
14 #1 SMP Wed Aug 28 17:19:38 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
Figure 1. .files/test.output
9. Makefile
Typing in all of these commands repeatedly is a hassle. To avoid that, we use a program called
gmake. Create a file called Makefile, as shown in Figure 3 (page 7).
Make sure that indented commands in a Makefile are indented with a TAB character, not spaces. If
you mistakenly use spaces to indent commands in a Makefile, you will get an error message. Proper
capitalization is also important. Now you can make, check in, and submit your program as follows :
bash-18$ rm hello.class
bash-19$ gmake ci
bash-20$ gmake all
bash-21$ gmake submit
To submit files directly from the command line without using the Makefile, the following command
may be used :
submit cmps012b-wm.f13 lab1 README Makefile hello.java
If you are doing pair programming, also submit the file PARTNER. The first argument to submit is the
name of the class volume, the second argument is the name of the project, and the rest are names of
files to be submitted.
CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 5 of 10
10. Verifying the submit
To check on the files you submitted, look in the directory
/afs/cats.ucsc.edu/class/cmps012b-wm.f13/lab1/$USER.
You won’t actually be able to read the files, but you can verify the filenames. Check to make sure
that you have submitted all the files that should be submitted.
In order to verify that your submit actually worked, create a new directory in your personal file
space, or choose an existing test submit directory and use rm to delete any existing files in that. Then
copy the files you submitted from your working directory into the new directory. Do not copy other
files. Did everything work as expected ?
You may use any system to which you have access as your development system. However, you must
test your program on one of the Linux servers or lab workstations prior to submitting it. Graders
will only use unix.ucsc.edu to do the grading.
11. Automating checkin and submit
You will note that the Makefile has two targets ci and submit. The purpose of make is to automate
routine boring tasks. So try checking in everything all at once and then submitting it :
bash-22$ gmake ci
bash-23$ gmake submit
Note that when this is automated, you don’t run the risk of forgetting a file when you submit.
12. WARNING
The time to figure out how to do it is NOT the day the first real assignment is due. Excuses sent late
on the due date will be rejected and your assignment will score ZERO. There is no excuse for not
knowing how to use submit and/or the Unix workarounds if the script does not work. Assignments
submitted via email will not be accepted. They only way an assignment will be submitted is via Unix
on or before the due date. You may submit an assignment as many times as you want BEFORE the
due date in order to ensure that something is submitted if there are last minute problems.
13. Miscellaneous
This section applies to all labs and programs submitted during the quarter. If you choose to do pair
programming, read the requirements in the subdirectory of the syllabus.
The README file should contain your name and username, the name of the host you used to do the
development, and any other necessary comments, such as the source of any code you did not write
yourself. To find out the name of the host you are currently using, use the command hostname.
You must also follow some basic source code formatting requirements that are checked up on by the
script checksource. You can locate it in the same manner as you did cid above. Reading assignment : /afs/cats.ucsc.edu/courses/cmps012b-wm/Coding-style/.
14. Prerequisites : Java and Unix
This course assumes you have had experience with Java and Unix. If not, you should read the first
seven chapters of Ja va by Dissection [http://www.lulu.com/javabydissection] and begin working
with Unix (you need a Unix reference book). This paragraph is just a slight roadmap to bring up
your Java skills if you have had a prerequisite course that used C or C++, or used some operating
system other than Unix.
UCSC has a subscription to Safari Books Online [http://proquest.safaribooksonline.com/], which is
maintained by the O’Reilly publishers [http://oreilly.com/]. You may read their books online for
free, provided you use a UCSC computer. Recommended readings : ‘‘Learning the Unix Operating
System’’, ‘‘Managing Projects with GNU Make’’, ‘‘Java in a Nutshell’’.
CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 6 of 10
15. Pair programming
If you are doing pair programming, carefully read over the summary in cmps012b-wm/Syllabus/pairprogramming. Note especially carefully the format of the PARTNER file. Use the partnercheck script to
check your PARTNER file before submitting it.
16. What to submit
Submit the files .cshrc, .bashrc, .bash_profile, README, Makefile, and hello.java.
There is a subdirectory called .score which contains instructions to the grader. Note that because it
begins with a dot, it is ‘‘hidden’’, and so will not show up as part of the output of the ls command,
unless the -a option is used. Similarly, there is another directory called .files, which is also hidden.
Neither of these show up if you are using a browser.
Do not submit any of the files generated by the script in this directory. However, you may want to do
a pre-grade in a private directory of your own in order to guess at what score you might receive.
Look for a similar directory in future labs and programs.
17. More on rc (dot) files
Figure 4 (page 8) shows some commands that you might want to incorporate into your ~/.bashrc file,
and Figure 5 (page 9) shows some commands that you might want to incorporate into your ~/.cshrc
file. They show how to customize the environment, make new convenience commands available, customize the prompt, etc. The man(1) pages for bash(1) and tcsh(1) will provide more information and
details. This section is informational only and is not part of this lab.
If you are not sure which shell you prefer using, and your default is /bin/tcsh, you can switch to bash
temporarily just by typing the command bash at the command prompt. To permanently make the
change, use the command chsh.
My suggestion is that you make bash your default shell, unless you have a preference for tcsh. Shell
scripts are almost exclusively written in bash or sh, and make always calls /bin/sh to process its commands. So if your interactive shell is bash, you only need to know one shell. And there are a few
things that are difficult to do in tcsh.
Refer to Tom Christiansen’s article ‘‘Csh Programming Considered Harmful’’ :
http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/
CMPS-012M • Fall 2013 • Lab 1 • Hello World in Java ; gmake ; RCS page 7 of 10
1 // $Id: hello.java,v 1.4 2013-03-27 12:35:02-07 – – $
2
3 //
4 // NAME
5 // hello – a verbose version of the classical “Hello World” program.
6 //
7 // SYNOPSIS
8 // hello
9 //
10 // DESCRIPTION
11 // Prints the message “Hello World” to stdout, and otherwise
12 // introduces itself and its environment.
13 //
14
15 import java.util.ArrayList;
16 import java.util.List;
17 import static java.lang.System.*;
18
19 class hello {
20
21 static void printprop (String format, String… properties) {
22 List