As a way of introducing CVS, we'll go through a typical work-session using CVS. The first thing to understand is that CVS stores all files in a centralized repository (see section 3 The Repository); this section assumes that a repository is set up.
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'.
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 5 Multiple developers, for an explanation.
When you have checked that the compiler is still compilable you decide to make a new version of `backend.c'. This will store your new `backend.c' in the repository and make it available to anyone else who is using that same repository.
$ 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 there is a default
which will vary with your operating system, for example
vi
for unix or notepad
for Windows
NT/95.
When CVS starts the editor, it includes a list of
files which are modified. For the CVS client,
this list is based on comparing the modification time
of the file against the modification time that the file
had when it was last gotten or updated. Therefore, if
a file's modification time has changed but its contents
have not, it will show up as modified. The simplest
way to handle this is simply not to worry about it--if
you proceed with the commit CVS will detect that
the contents are not modified and treat it as an
unmodified file. The next update
will clue
CVS in to the fact that the file is unmodified,
and it will reset its stored timestamp so that the file
will not show up in future editor sessions.
If you want to avoid 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
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 A.15 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 C.10 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 C.9 Ignoring files via cvsignore,
for information about how to make that warning go away.
See section A.15.2 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.
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 done $ 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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