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A sample session

This section describes a typical work-session using CVS. It assumes that a repository is set up (see section The Repository).

Suppose you are working on a simple compiler. The source consists of a handful of C files and a `Makefile'. The compiler is called `tc' (Trivial Compiler), and the repository is set up so that there is a module called `tc'.

Getting the source

The first thing you must do is to get your own working copy of the source for `tc'. For this, you use the checkout command:

$ cvs checkout tc

This will create a new directory called `tc' and populate it with the source files.

$ cd tc
$ ls
CVS         Makefile    backend.c   driver.c    frontend.c  parser.c

The `CVS' directory is used internally by CVS. Normally, you should not modify or remove any of the files in it.

You start your favorite editor, hack away at `backend.c', and a couple of hours later you have added an optimization pass to the compiler. A note to RCS and SCCS users: There is no need to lock the files that you want to edit. See section Multiple developers for an explanation.

Committing your changes

When you have checked that the compiler is still compilable you decide to make a new version of `backend.c'.

$ cvs commit backend.c

CVS starts an editor, to allow you to enter a log message. You type in "Added an optimization pass.", save the temporary file, and exit the editor.

The environment variable $CVSEDITOR determines which editor is started. If $CVSEDITOR is not set, then if the environment variable $EDITOR is set, it will be used. If both $CVSEDITOR and $EDITOR are not set then the editor defaults to vi. If you want to avoid the overhead of starting an editor you can specify the log message on the command line using the `-m' flag instead, like this:

$ cvs commit -m "Added an optimization pass" backend.c

Cleaning up

Before you turn to other tasks you decide to remove your working copy of tc. One acceptable way to do that is of course

$ cd ..
$ rm -r tc

but a better way is to use the release command (see section release--Indicate that a Module is no longer in use):

$ cd ..
$ cvs release -d tc
M driver.c
? tc
You have [1] altered files in this repository.
Are you sure you want to release (and delete) module `tc': n
** `release' aborted by user choice.

The release command checks that all your modifications have been committed. If history logging is enabled it also makes a note in the history file. See section The history file.

When you use the `-d' flag with release, it also removes your working copy.

In the example above, the release command wrote a couple of lines of output. `? tc' means that the file `tc' is unknown to CVS. That is nothing to worry about: `tc' is the executable compiler, and it should not be stored in the repository. See section Ignoring files via cvsignore, for information about how to make that warning go away. See section release output, for a complete explanation of all possible output from release.

`M driver.c' is more serious. It means that the file `driver.c' has been modified since it was checked out.

The release command always finishes by telling you how many modified files you have in your working copy of the sources, and then asks you for confirmation before deleting any files or making any note in the history file.

You decide to play it safe and answer n RET when release asks for confirmation.

Viewing differences

You do not remember modifying `driver.c', so you want to see what has happened to that file.

$ cd tc
$ cvs diff driver.c

This command runs diff to compare the version of `driver.c' that you checked out with your working copy. When you see the output you remember that you added a command line option that enabled the optimization pass. You check it in, and release the module.

$ cvs commit -m "Added an optimization pass" driver.c
Checking in driver.c;
/usr/local/cvsroot/tc/driver.c,v  <--  driver.c
new revision: 1.2; previous revision: 1.1
$ cd ..
$ cvs release -d tc
? tc
You have [0] altered files in this repository.
Are you sure you want to release (and delete) module `tc': y

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