CS311 – Lecture 08 Outline

• Subversion (SVN)

*All information taken from “SVN Book” O’Reilly

Lecture 08 1CS 311 - Operating Systems I

Software needed

• SVN is installed in flip server• Windows users use Tortoise SVN.• Linux and MAC users visit this website for

installation instructions. - http://subversion.tigris.org/

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What is SVN?• Centralized system for sharing information.• Data stored in the system in the form of a file

system tree.• Any number of users with access to the

system can read-write data.• When user writes data into repository it

becomes publicly available.

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Difference between file server

• What happens when a user updates a file which is already being accessed by another?

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Problems with file sharing

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Lock-Modify-Unlock

• What are the problems with this model?Lecture 08 6CS 311 - Operating Systems I

Problems with Lock-Modify-Unlock

• Administrative problems• Unnecessary serialization• Creates a false sense of security• Restrictive

Lecture 08 7CS 311 - Operating Systems I

Copy-Modify-Merge solution

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Copy-Modify-Merge Solution

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Merits and demerits of copy-modify-merge solution

• Merits– No problem of serialization.– Administering the files much easier.– Resolving conflicts

• Demerits– Not all type of files can be merged (Eg. Audio)

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Subversion Uses copy-modify-merge system but still occasionally

implements locks on a file. Very helpful for collaborative work. In-built tools to view changes in a file and resolve

conflicts. Ability to browse through every revisions a file has

gone through and also revert to any revision. In-built tools to merge changes.

Lecture 08 11CS 311 - Operating Systems I

SVN Repository and Working Copy

• Repository is a place in the file system where all data exists.

• Working copy is a place in the file system where modifications are done to the data and then updated to the repository.

• To get a working copy use “svn checkout path-to-repository”.

• If the repository resides on a network use “http://path-to-repository” or if in a local system use “file:///path-to-repo”.

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Working Copies “.svn” folder in the working copy called the

administrative directory. It holds all changes, outdated revisions, the

information about the working copy, etc. To get the info about working copy use “svn info” from

inside the working copy.$ svn checkout http://svn.example.com/repos/calcA calc/Makefile (“A” means files are added)A calc/integer.cA calc/button.cChecked out revision 56.$ ls -A calcMakefile button.c integer.c .svn/

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Publishing changes

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To publish changes use “svn commit”$ svn commit button.c -m "Fixed a typo in button.c."Sending button.cTransmitting file data .Committed revision 57.

When your teammates now update their working copies using “svn update”$ svn updateU button.cUpdated to revision 57.

Always remember to update your working copy before committing changes to avoid conflicts.

How working copy tracks changes

.svn folder is the administrative folder. It keeps track of these

What revision are your files currently on Last update of working copy

“svn log” command gives you the history of changes.

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Creating a SVN Repository

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• To create a SVN repository usesvnadmin create repo-nameEx: svnadmin create /var/svn/newrepos

• To add files into the repository usesvn import files path-to-reposvn import mytree file:///var/svn/newrepos/some/project -m "Initial import"Adding mytree/bar.cAdding mytree/subdirAdding mytree/subdir/quux.hCommitted revision 1.

Making changes to repository To inform svn repo that you are making changes use the

svn command. svn add file #add file to repo svn delete file #delete file from repo svn copy file1 file2 svn move file1 file2 svn mkdir folder

After making all changes to repository do not forget to commit the changes (svn commit)

Use svn help command to know more about commands.

Lecture 08 17CS 311 - Operating Systems I

Status of files in working copy

• To know the status of files in the working copy use command “svn status”– ? scratch.c # file is not under version control– A stuff/loot/bloo.h # file is scheduled for

addition– C stuff/loot/lump.c # file has textual conflicts

from an update– D stuff/fish.c # file is scheduled for deletion– M bar.c # the content in bar.c has local

modificationsLecture 08 CS 311 - Operating Systems I 18

Using svn diff• diff finds the modifications done to a file.• Also used to generate patch. (svn diff file > patch)$ svn diff bar.c--- bar.c (revision 3)+++ bar.c (working copy)@@ -1,3 +1,2 @@+#include <stdio.h>int main(void) {- printf("Sixty-four slices of American Cheese...\n");+ printf("Sixty-five slices of American Cheese...\n");return 0;}

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