Using UNIX groups and CVS

1
Object-Oriented Software Engineering

• Using UNIX groups and CVS

2
Unix Groups

• You should now have been placed in a Unix group
  on the GAUL system
• Everyone in your project group (team) should be
  in the same Unix group
• This means that you can share files with your
  group members without letting members of other
  groups see them
• You will want to do this for the final code
  submission directory
• We will look at sever command
• groups for seeing what Unix groups you are in
• chgrp for assigning the group ownership of a
  file
• chmod for permitting group members to access a
  file

3
Your Unix Groups

• To find what Unix groups you are in, issue the
  command groups
• You should see a group name with the string CS212
  in it
• E.g CS212-YXX where Y is your section number 1or
  2 and XX is your group number 07 for group 7
• This is the Unix group that all the members of
  your project group are in
• You should also see a group name indicating that
  you are in an undergrad course (e.g. 2ndyr or
  undrgrad)
• This is your default group, but does not matter
  for CS 212 purposes

4
Giving a File to Your Group

• Permitting a file to your Unix group has two
  stages
• Change the group ownership of the file
• Permit it to group
• Every file has two owners
• A user (I.e. you, for your files)
• A Unix group
• By default, your default Unix group is the group
  owner of your files
• To change the Unix group of a file or files,
  issue the command chgrp group file, where
• group is the Unix group you want to change it to
• file is the name of the file
• Example to give ownership of QueueTypes.h to
  group CS212-YXX chgrp CS212-YXX QueueTypes.h
• You can do more than one file this way
  e.g. chgrp CS212-YXX .c .o

5
Checking Group Ownership

• To see what group a file belongs to
• Issue the command ls lg file
• This will list the group owner after the user
  owner
• Example cartier issues command ls lg
  QueueTypes.h
• System responds with something like
• -rw------- 1 cartier CS212-YXX 258 Oct 17 0959
  QueueType.h
• CS212-YXX is the group owner
• A file can only have one group owner to change
  it, just use the chgrp command again with a
  different group name
• To restore default group ownership to a file,
  just make a copy of it and delete the original
• But using only the chgrp command is still not
  sufficient to let other members of your group to
  see the file
• It is necessary to permit thefile by changing
  the access mode of the file

6
Permitting Your Group Access

• To let the members of a Unix group see a file
  owned by that Unix group, issue the command chmod
  grw file
• This permits the group (g) to have read access
  (r) to file
• It also permits the group (g) to execute (x) file
  it is already executable
• You can do this on multiple files too
• Example
• cartier issues command chmod grx QueueTypes.h
• Then cartier issues command ls lg QueueTypes.h
• System should give something like-rw-r----- 1
  cartier CS212-YXX 258 Oct 17 0959 QueueType.h
• The second r in rw-r----- indicates that the
  group now has access
• People outside the Unix group (others) do not
  have read access unless you also say chmod orx
  file

7
Permitting Access to Directories

• Note to give access to a file in a directory,
  you have to chgrp and chmod the directory too!
• Option R on chgrp and chmod will do it
  recursively on all members of the directory
• Example from home directory cartier says chgrp
  R CS212-YXX project chmod R grx project
• Directory project and everything in it now
  accessible to group CS212-YXX
• For more details on how to permit files other
  different ways, see man chmod

8
Summary

• User cartier does groups
• System response with 2ndyr CS212-YXX
• cartier now does chgrp R CS212-YXX
  project chmod R grx project cd project ls
  lg QueueTypes.h
• System responds with something like -rw-r-----
  1 cartier CS212-YXX 251 Oct 17 0959
  QueueTypes.h
• User bolivar (in the same group) does groups
• System responds with 3rdyr CS212-YXX
• bolivar now does cd cartier/project
• User bolivar will now be able to read
  QueueTypes.h

9
Code Repositories

• Repository for code is used when coding with
  other team members, where you share the code.
• Your whole team has access to the repository. The
  latest version of ALL of the code is stored in
  the repository, if you need to make changes, you
  check out ONLY the pieces you will use to make
  the changes and test the changes, change the
  code, and then check it back in.
• CVS is a code repository that is optimistic (it
  assumes that conflicts are rare). Thus, it allows
  any member of the team to make changes to any
  piece he/she has access to. Since two team
  members can commit changes to the same resource,
  conflicts must be resolved by the second
  committer.

10
Revision Control The Problem

• Take a software project where
• There are several files with several people
  working on those files
• You want one final version of everything
• Possible Problems
• Different people having different versions of
  files
• Inconsistent changes by different people
• Changes getting lost

11
Example 1 Conflicting Changes

• Bob has master copy of the files Person.java and
  Address.java
• Alice and Chris get copies of both files
• Alice changes Person.java and Chris changes
  Address.java (everything still works for them)
• Alice copies Person.java back to Bobs area, Chris
  copies Address.java back to Bobs area
• Bob tries but cant compile the program anymore
• Now there is no working master copy!

12
Example 2 Changes Getting Lost

• Alice and Chris both change Person.java
• Chris sends his copy to Bob
• Later, Alice sends her changes to Bob
• Finally, Chris gets Alices changes from Bob
• Now no one has Chriss original changes!

13
Minimizing Problems

• ALWAYS FOLLOW THESE STEPS
• Start fresh ? Before starting anywork, update
  all the files in your workspace with the latest
  updates (In eclipse you right click on the
  project in CVS Repository View and select
  Checkout)
• Run your unit tests ? Make sure they all pass, if
  the system is broken before you start and you
  start making changes, you wont know if your
  changes broke it, or there were previous problems
• Make changes ? Do all your editing in your local
  workspace. Debug until everything works
• Run the unit tests again ? Make sure your changes
  didnt break any of the other components that you
  werent even working on.
• Synchronize ? When you are ready to commit,
  synchronize. Check incoming changes and add them
  to your files. Resolve changes. Rerun your unit
  tests to make sure everything is still correct.
  THEN COMMIT YOUR CHANGES!

14
Terminology

• Check Out ? checks out all the files in the
  project
• Update ? gets the latest version from the
  repository and inserts it into your stuff (you
  should always do this first)
• Sync with repository ? Shows the modifications
  between the latest version in the repository and
  the changes you have made
• Commit ? takes your current file and writes it to
  the repository (so this will be the new master
  copy)

15

• When you Sync with Repository, you will see
  something like this
• This shows the changes, resolve the changes and
  then sync again, then commit when you have no
  changes.

16
Step 1 Create a Repository

• Have one person create an initial repository on
  Gaul
• In unix, create a directory that will be the
  repository
• Change the permissions on that directory so your
  group can access it.
• Go to that directory and type pwd to find the
  absolute path
• Type cvs with the absolute path and then init as
  below cvs d /gaul/u0//youruserid/repositorydi
  rectory init
• Build the repository in Eclipse (build a project,
  add some files, then go to the CVS perspective to
  attach your files to the repository)
• Have your group members attach to your repository
  in Eclipse (we will do this in our workshop on
  Thursday, Feb 23 in PB 225)

17
Change the permission on the directories

• Make sure that the user who creates the
  repository on Gaul changes the permission and
  groups on the appropriate directories
• NOTE I read that you have to do a chmod like
  this
• chmod grws (set the setgid bit default
  group id- now files created in the directory will
  have the same group as the directory NOT the
  default group)

18
Share Projects

• Note A file is flagged as either ASCII or
  Binary, this is important when CVS displays the
  line-by-line changes. In most cases, text files
  should be ASCII
• To share the project
• Right click on the project in Navigator view
  (Window Show View Navigator) and select
  Team, then select Share Project. Just leave the
  name the same as the project name.
• Commit the files in the project to the repository

19
Bring in Another User

• Another user wants to use files in the
  repository, so he/she would
• Open the CVS Perspective
• Right click in the window and select new
  Repository Location
• Type in the same machine (gaul) and absolute
  path, but his/her own userid and password
• Then expand the repository location, then expand
  HEAD and you should see the project. Right click
  on the project and choose Checkout As Project,
  select Navigator view and now the other user sees
  the project.