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This is cvs.info, produced by makeinfo version 4.0 from cvs.texinfo. START-INFO-DIR-ENTRY * CVS: (cvs). Concurrent Versions System END-INFO-DIR-ENTRY Copyright (C) 1992, 1993 Signum Support AB Copyright (C) 1993, 1994 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation. File: cvs.info, Node: Top, Next: Overview, Up: (dir) This info manual describes how to use and administer CVS version 1.11.1p1. * Menu: * Overview:: An introduction to CVS * Repository:: Where all your sources are stored * Starting a new project:: Starting a project with CVS * Revisions:: Numeric and symbolic names for revisions * Branching and merging:: Diverging/rejoining branches of development * Recursive behavior:: CVS descends directories * Adding and removing:: Adding/removing/renaming files/directories * History browsing:: Viewing the history of files in various ways CVS and the Real World. ----------------------- * Binary files:: CVS can handle binary files * Multiple developers:: How CVS helps a group of developers * Revision management:: Policy questions for revision management * Keyword substitution:: CVS can include the revision inside the file * Tracking sources:: Tracking third-party sources * Builds:: Issues related to CVS and builds * Special Files:: Devices, links and other non-regular files References. ----------- * CVS commands:: CVS commands share some things * Invoking CVS:: Quick reference to CVS commands * Administrative files:: Reference manual for the Administrative files * Environment variables:: All environment variables which affect CVS * Compatibility:: Upgrading CVS versions * Troubleshooting:: Some tips when nothing works * Credits:: Some of the contributors to this manual * BUGS:: Dealing with bugs in CVS or this manual * Index:: Index File: cvs.info, Node: Overview, Next: Repository, Prev: Top, Up: Top Overview ******** This chapter is for people who have never used CVS, and perhaps have never used version control software before. If you are already familiar with CVS and are just trying to learn a particular feature or remember a certain command, you can probably skip everything here. * Menu: * What is CVS?:: What you can do with CVS * What is CVS not?:: Problems CVS doesn't try to solve * A sample session:: A tour of basic CVS usage File: cvs.info, Node: What is CVS?, Next: What is CVS not?, Up: Overview What is CVS? ============ CVS is a version control system. Using it, you can record the history of your source files. For example, bugs sometimes creep in when software is modified, and you might not detect the bug until a long time after you make the modification. With CVS, you can easily retrieve old versions to see exactly which change caused the bug. This can sometimes be a big help. You could of course save every version of every file you have ever created. This would however waste an enormous amount of disk space. CVS stores all the versions of a file in a single file in a clever way that only stores the differences between versions. CVS also helps you if you are part of a group of people working on the same project. It is all too easy to overwrite each others' changes unless you are extremely careful. Some editors, like GNU Emacs, try to make sure that the same file is never modified by two people at the same time. Unfortunately, if someone is using another editor, that safeguard will not work. CVS solves this problem by insulating the different developers from each other. Every developer works in his own directory, and CVS merges the work when each developer is done. CVS started out as a bunch of shell scripts written by Dick Grune, posted to the newsgroup `comp.sources.unix' in the volume 6 release of December, 1986. While no actual code from these shell scripts is present in the current version of CVS much of the CVS conflict resolution algorithms come from them. In April, 1989, Brian Berliner designed and coded CVS. Jeff Polk later helped Brian with the design of the CVS module and vendor branch support. You can get CVS in a variety of ways, including free download from the internet. For more information on downloading CVS and other CVS topics, see: http://www.cvshome.org/ http://www.loria.fr/~molli/cvs-index.html There is a mailing list, known as `info-cvs', devoted to CVS. To subscribe or unsubscribe write to `info-cvs-request@gnu.org'. If you prefer a usenet group, the right group is `comp.software.config-mgmt' which is for CVS discussions (along with other configuration management systems). In the future, it might be possible to create a `comp.software.config-mgmt.cvs', but probably only if there is sufficient CVS traffic on `comp.software.config-mgmt'. You can also subscribe to the bug-cvs mailing list, described in more detail in *Note BUGS::. To subscribe send mail to bug-cvs-request@gnu.org. File: cvs.info, Node: What is CVS not?, Next: A sample session, Prev: What is CVS?, Up: Overview What is CVS not? ================ CVS can do a lot of things for you, but it does not try to be everything for everyone. CVS is not a build system. Though the structure of your repository and modules file interact with your build system (e.g. `Makefile's), they are essentially independent. CVS does not dictate how you build anything. It merely stores files for retrieval in a tree structure you devise. CVS does not dictate how to use disk space in the checked out working directories. If you write your `Makefile's or scripts in every directory so they have to know the relative positions of everything else, you wind up requiring the entire repository to be checked out. If you modularize your work, and construct a build system that will share files (via links, mounts, `VPATH' in `Makefile's, etc.), you can arrange your disk usage however you like. But you have to remember that _any_ such system is a lot of work to construct and maintain. CVS does not address the issues involved. Of course, you should place the tools created to support such a build system (scripts, `Makefile's, etc) under CVS. Figuring out what files need to be rebuilt when something changes is, again, something to be handled outside the scope of CVS. One traditional approach is to use `make' for building, and use some automated tool for generating the dependencies which `make' uses. See *Note Builds::, for more information on doing builds in conjunction with CVS. CVS is not a substitute for management. Your managers and project leaders are expected to talk to you frequently enough to make certain you are aware of schedules, merge points, branch names and release dates. If they don't, CVS can't help. CVS is an instrument for making sources dance to your tune. But you are the piper and the composer. No instrument plays itself or writes its own music. CVS is not a substitute for developer communication. When faced with conflicts within a single file, most developers manage to resolve them without too much effort. But a more general definition of "conflict" includes problems too difficult to solve without communication between developers. CVS cannot determine when simultaneous changes within a single file, or across a whole collection of files, will logically conflict with one another. Its concept of a "conflict" is purely textual, arising when two changes to the same base file are near enough to spook the merge (i.e. `diff3') command. CVS does not claim to help at all in figuring out non-textual or distributed conflicts in program logic. For example: Say you change the arguments to function `X' defined in file `A'. At the same time, someone edits file `B', adding new calls to function `X' using the old arguments. You are outside the realm of CVS's competence. Acquire the habit of reading specs and talking to your peers. CVS does not have change control Change control refers to a number of things. First of all it can mean "bug-tracking", that is being able to keep a database of reported bugs and the status of each one (is it fixed? in what release? has the bug submitter agreed that it is fixed?). For interfacing CVS to an external bug-tracking system, see the `rcsinfo' and `verifymsg' files (*note Administrative files::). Another aspect of change control is keeping track of the fact that changes to several files were in fact changed together as one logical change. If you check in several files in a single `cvs commit' operation, CVS then forgets that those files were checked in together, and the fact that they have the same log message is the only thing tying them together. Keeping a GNU style `ChangeLog' can help somewhat. Another aspect of change control, in some systems, is the ability to keep track of the status of each change. Some changes have been written by a developer, others have been reviewed by a second developer, and so on. Generally, the way to do this with CVS is to generate a diff (using `cvs diff' or `diff') and email it to someone who can then apply it using the `patch' utility. This is very flexible, but depends on mechanisms outside CVS to make sure nothing falls through the cracks. CVS is not an automated testing program It should be possible to enforce mandatory use of a testsuite using the `commitinfo' file. I haven't heard a lot about projects trying to do that or whether there are subtle gotchas, however. CVS does not have a builtin process model Some systems provide ways to ensure that changes or releases go through various steps, with various approvals as needed. Generally, one can accomplish this with CVS but it might be a little more work. In some cases you'll want to use the `commitinfo', `loginfo', `rcsinfo', or `verifymsg' files, to require that certain steps be performed before cvs will allow a checkin. Also consider whether features such as branches and tags can be used to perform tasks such as doing work in a development tree and then merging certain changes over to a stable tree only once they have been proven. File: cvs.info, Node: A sample session, Prev: What is CVS not?, Up: Overview A sample session ================ 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" (*note 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'. * Menu: * Getting the source:: Creating a workspace * Committing your changes:: Making your work available to others * Cleaning up:: Cleaning up * Viewing differences:: Viewing differences File: cvs.info, Node: Getting the source, Next: Committing your changes, Up: A sample session 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. *Note Multiple developers::, for an explanation. File: cvs.info, Node: Committing your changes, Next: Cleaning up, Prev: Getting the source, Up: A sample session Committing your changes ----------------------- 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 `$EDITOR' are not set then there is a default which will vary with your operating system, for example `vi' for unix or `notepad' for Windows NT/95. In addition, CVS checks the `$VISUAL' environment variable. Opinions vary on whether this behavior is desirable and whether future releases of CVS should check `$VISUAL' or ignore it. You will be OK either way if you make sure that `$VISUAL' is either unset or set to the same thing as `$EDITOR'. 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 File: cvs.info, Node: Cleaning up, Next: Viewing differences, Prev: Committing your changes, Up: A sample session 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 (*note release::): $ 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) directory `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. *Note 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. *Note cvsignore::, for information about how to make that warning go away. *Note 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. File: cvs.info, Node: Viewing differences, Prev: Cleaning up, Up: A sample session 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 done $ cd .. $ cvs release -d tc ? tc You have [0] altered files in this repository. Are you sure you want to release (and delete) directory `tc': y File: cvs.info, Node: Repository, Next: Starting a new project, Prev: Overview, Up: Top The Repository ************** The CVS "repository" stores a complete copy of all the files and directories which are under version control. Normally, you never access any of the files in the repository directly. Instead, you use CVS commands to get your own copy of the files into a "working directory", and then work on that copy. When you've finished a set of changes, you check (or "commit") them back into the repository. The repository then contains the changes which you have made, as well as recording exactly what you changed, when you changed it, and other such information. Note that the repository is not a subdirectory of the working directory, or vice versa; they should be in separate locations. CVS can access a repository by a variety of means. It might be on the local computer, or it might be on a computer across the room or across the world. To distinguish various ways to access a repository, the repository name can start with an "access method". For example, the access method `:local:' means to access a repository directory, so the repository `:local:/usr/local/cvsroot' means that the repository is in `/usr/local/cvsroot' on the computer running CVS. For information on other access methods, see *Note Remote repositories::. If the access method is omitted, then if the repository does not contain `:', then `:local:' is assumed. If it does contain `:' then either `:ext:' or `:server:' is assumed. For example, if you have a local repository in `/usr/local/cvsroot', you can use `/usr/local/cvsroot' instead of `:local:/usr/local/cvsroot'. But if (under Windows NT, for example) your local repository is `c:\src\cvsroot', then you must specify the access method, as in `:local:c:\src\cvsroot'. The repository is split in two parts. `$CVSROOT/CVSROOT' contains administrative files for CVS. The other directories contain the actual user-defined modules. * Menu: * Specifying a repository:: Telling CVS where your repository is * Repository storage:: The structure of the repository * Working directory storage:: The structure of working directories * Intro administrative files:: Defining modules * Multiple repositories:: Multiple repositories * Creating a repository:: Creating a repository * Backing up:: Backing up a repository * Moving a repository:: Moving a repository * Remote repositories:: Accessing repositories on remote machines * Read-only access:: Granting read-only access to the repository * Server temporary directory:: The server creates temporary directories File: cvs.info, Node: Specifying a repository, Next: Repository storage, Up: Repository Telling CVS where your repository is ==================================== There are several ways to tell CVS where to find the repository. You can name the repository on the command line explicitly, with the `-d' (for "directory") option: cvs -d /usr/local/cvsroot checkout yoyodyne/tc Or you can set the `$CVSROOT' environment variable to an absolute path to the root of the repository, `/usr/local/cvsroot' in this example. To set `$CVSROOT', `csh' and `tcsh' users should have this line in their `.cshrc' or `.tcshrc' files: setenv CVSROOT /usr/local/cvsroot `sh' and `bash' users should instead have these lines in their `.profile' or `.bashrc': CVSROOT=/usr/local/cvsroot export CVSROOT A repository specified with `-d' will override the `$CVSROOT' environment variable. Once you've checked a working copy out from the repository, it will remember where its repository is (the information is recorded in the `CVS/Root' file in the working copy). The `-d' option and the `CVS/Root' file both override the `$CVSROOT' environment variable. If `-d' option differs from `CVS/Root', the former is used. Of course, for proper operation they should be two ways of referring to the same repository. File: cvs.info, Node: Repository storage, Next: Working directory storage, Prev: Specifying a repository, Up: Repository How data is stored in the repository ==================================== For most purposes it isn't important _how_ CVS stores information in the repository. In fact, the format has changed in the past, and is likely to change in the future. Since in almost all cases one accesses the repository via CVS commands, such changes need not be disruptive. However, in some cases it may be necessary to understand how CVS stores data in the repository, for example you might need to track down CVS locks (*note Concurrency::) or you might need to deal with the file permissions appropriate for the repository. * Menu: * Repository files:: What files are stored in the repository * File permissions:: File permissions * Windows permissions:: Issues specific to Windows * Attic:: Some files are stored in the Attic * CVS in repository:: Additional information in CVS directory * Locks:: CVS locks control concurrent accesses * CVSROOT storage:: A few things about CVSROOT are different File: cvs.info, Node: Repository files, Next: File permissions, Up: Repository storage Where files are stored within the repository -------------------------------------------- The overall structure of the repository is a directory tree corresponding to the directories in the working directory. For example, supposing the repository is in /usr/local/cvsroot here is a possible directory tree (showing only the directories): /usr | +--local | | | +--cvsroot | | | | | +--CVSROOT | (administrative files) | +--gnu | | | +--diff | | (source code to GNU diff) | | | +--rcs | | (source code to RCS) | | | +--cvs | (source code to CVS) | +--yoyodyne | +--tc | | | +--man | | | +--testing | +--(other Yoyodyne software) With the directories are "history files" for each file under version control. The name of the history file is the name of the corresponding file with `,v' appended to the end. Here is what the repository for the `yoyodyne/tc' directory might look like: `$CVSROOT' | +--yoyodyne | | | +--tc | | | +--Makefile,v +--backend.c,v +--driver.c,v +--frontend.c,v +--parser.c,v +--man | | | +--tc.1,v | +--testing | +--testpgm.t,v +--test2.t,v The history files contain, among other things, enough information to recreate any revision of the file, a log of all commit messages and the user-name of the person who committed the revision. The history files are known as "RCS files", because the first program to store files in that format was a version control system known as RCS. For a full description of the file format, see the `man' page `rcsfile(5)', distributed with RCS, or the file `doc/RCSFILES' in the CVS source distribution. This file format has become very common--many systems other than CVS or RCS can at least import history files in this format. The RCS files used in CVS differ in a few ways from the standard format. The biggest difference is magic branches; for more information see *Note Magic branch numbers::. Also in CVS the valid tag names are a subset of what RCS accepts; for CVS's rules see *Note Tags::. File: cvs.info, Node: File permissions, Next: Windows permissions, Prev: Repository files, Up: Repository storage File permissions ---------------- All `,v' files are created read-only, and you should not change the permission of those files. The directories inside the repository should be writable by the persons that have permission to modify the files in each directory. This normally means that you must create a UNIX group (see group(5)) consisting of the persons that are to edit the files in a project, and set up the repository so that it is that group that owns the directory. This means that you can only control access to files on a per-directory basis. Note that users must also have write access to check out files, because CVS needs to create lock files (*note Concurrency::). Also note that users must have write access to the `CVSROOT/val-tags' file. CVS uses it to keep track of what tags are valid tag names (it is sometimes updated when tags are used, as well as when they are created). Each RCS file will be owned by the user who last checked it in. This has little significance; what really matters is who owns the directories. CVS tries to set up reasonable file permissions for new directories that are added inside the tree, but you must fix the permissions manually when a new directory should have different permissions than its parent directory. If you set the `CVSUMASK' environment variable that will control the file permissions which CVS uses in creating directories and/or files in the repository. `CVSUMASK' does not affect the file permissions in the working directory; such files have the permissions which are typical for newly created files, except that sometimes CVS creates them read-only (see the sections on watches, *Note Setting a watch::; -r, *Note Global options::; or `CVSREAD', *Note Environment variables::). Note that using the client/server CVS (*note Remote repositories::), there is no good way to set `CVSUMASK'; the setting on the client machine has no effect. If you are connecting with `rsh', you can set `CVSUMASK' in `.bashrc' or `.cshrc', as described in the documentation for your operating system. This behavior might change in future versions of CVS; do not rely on the setting of `CVSUMASK' on the client having no effect. Using pserver, you will generally need stricter permissions on the CVSROOT directory and directories above it in the tree; see *Note Password authentication security::. Some operating systems have features which allow a particular program to run with the ability to perform operations which the caller of the program could not. For example, the set user ID (setuid) or set group ID (setgid) features of unix or the installed image feature of VMS. CVS was not written to use such features and therefore attempting to install CVS in this fashion will provide protection against only accidental lapses; anyone who is trying to circumvent the measure will be able to do so, and depending on how you have set it up may gain access to more than just CVS. You may wish to instead consider pserver. It shares some of the same attributes, in terms of possibly providing a false sense of security or opening security holes wider than the ones you are trying to fix, so read the documentation on pserver security carefully if you are considering this option (*Note Password authentication security::). File: cvs.info, Node: Windows permissions, Next: Attic, Prev: File permissions, Up: Repository storage File Permission issues specific to Windows ------------------------------------------ Some file permission issues are specific to Windows operating systems (Windows 95, Windows NT, and presumably future operating systems in this family. Some of the following might apply to OS/2 but I'm not sure). If you are using local CVS and the repository is on a networked file system which is served by the Samba SMB server, some people have reported problems with permissions. Enabling WRITE=YES in the samba configuration is said to fix/workaround it. Disclaimer: I haven't investigated enough to know the implications of enabling that option, nor do I know whether there is something which CVS could be doing differently in order to avoid the problem. If you find something out, please let us know as described in *Note BUGS::. File: cvs.info, Node: Attic, Next: CVS in repository, Prev: Windows permissions, Up: Repository storage The attic --------- You will notice that sometimes CVS stores an RCS file in the `Attic'. For example, if the CVSROOT is `/usr/local/cvsroot' and we are talking about the file `backend.c' in the directory `yoyodyne/tc', then the file normally would be in /usr/local/cvsroot/yoyodyne/tc/backend.c,v but if it goes in the attic, it would be in /usr/local/cvsroot/yoyodyne/tc/Attic/backend.c,v instead. It should not matter from a user point of view whether a file is in the attic; CVS keeps track of this and looks in the attic when it needs to. But in case you want to know, the rule is that the RCS file is stored in the attic if and only if the head revision on the trunk has state `dead'. A `dead' state means that file has been removed, or never added, for that revision. For example, if you add a file on a branch, it will have a trunk revision in `dead' state, and a branch revision in a non-`dead' state. File: cvs.info, Node: CVS in repository, Next: Locks, Prev: Attic, Up: Repository storage The CVS directory in the repository ----------------------------------- The `CVS' directory in each repository directory contains information such as file attributes (in a file called `CVS/fileattr'. In the future additional files may be added to this directory, so implementations should silently ignore additional files. This behavior is implemented only by CVS 1.7 and later; for details see *Note Watches Compatibility::. The format of the fileattr file is a series of entries of the following form (where `{' and `}' means the text between the braces can be repeated zero or more times): ENT-TYPE FILENAME <tab> ATTRNAME = ATTRVAL {; ATTRNAME = ATTRVAL} <linefeed> ENT-TYPE is `F' for a file, in which case the entry specifies the attributes for that file. ENT-TYPE is `D', and FILENAME empty, to specify default attributes to be used for newly added files. Other ENT-TYPE are reserved for future expansion. CVS 1.9 and older will delete them any time it writes file attributes. CVS 1.10 and later will preserve them. Note that the order of the lines is not significant; a program writing the fileattr file may rearrange them at its convenience. There is currently no way of quoting tabs or linefeeds in the filename, `=' in ATTRNAME, `;' in ATTRVAL, etc. Note: some implementations also don't handle a NUL character in any of the fields, but implementations are encouraged to allow it. By convention, ATTRNAME starting with `_' is for an attribute given special meaning by CVS; other ATTRNAMEs are for user-defined attributes (or will be, once implementations start supporting user-defined attributes). Builtin attributes: `_watched' Present means the file is watched and should be checked out read-only. `_watchers' Users with watches for this file. Value is WATCHER > TYPE { , WATCHER > TYPE } where WATCHER is a username, and TYPE is zero or more of edit,unedit,commit separated by `+' (that is, nothing if none; there is no "none" or "all" keyword). `_editors' Users editing this file. Value is EDITOR > VAL { , EDITOR > VAL } where EDITOR is a username, and VAL is TIME+HOSTNAME+PATHNAME, where TIME is when the `cvs edit' command (or equivalent) happened, and HOSTNAME and PATHNAME are for the working directory. Example: Ffile1 _watched=;_watchers=joe>edit,mary>commit Ffile2 _watched=;_editors=sue>8 Jan 1975+workstn1+/home/sue/cvs D _watched= means that the file `file1' should be checked out read-only. Furthermore, joe is watching for edits and mary is watching for commits. The file `file2' should be checked out read-only; sue started editing it on 8 Jan 1975 in the directory `/home/sue/cvs' on the machine `workstn1'. Future files which are added should be checked out read-only. To represent this example here, we have shown a space after `D', `Ffile1', and `Ffile2', but in fact there must be a single tab character there and no spaces. File: cvs.info, Node: Locks, Next: CVSROOT storage, Prev: CVS in repository, Up: Repository storage CVS locks in the repository --------------------------- For an introduction to CVS locks focusing on user-visible behavior, see *Note Concurrency::. The following section is aimed at people who are writing tools which want to access a CVS repository without interfering with other tools acessing the same repository. If you find yourself confused by concepts described here, like "read lock", "write lock", and "deadlock", you might consult the literature on operating systems or databases. Any file in the repository with a name starting with `#cvs.rfl.' is a read lock. Any file in the repository with a name starting with `#cvs.wfl' is a write lock. Old versions of CVS (before CVS 1.5) also created files with names starting with `#cvs.tfl', but they are not discussed here. The directory `#cvs.lock' serves as a master lock. That is, one must obtain this lock first before creating any of the other locks. To obtain a readlock, first create the `#cvs.lock' directory. This operation must be atomic (which should be true for creating a directory under most operating systems). If it fails because the directory already existed, wait for a while and try again. After obtaining the `#cvs.lock' lock, create a file whose name is `#cvs.rfl.' followed by information of your choice (for example, hostname and process identification number). Then remove the `#cvs.lock' directory to release the master lock. Then proceed with reading the repository. When you are done, remove the `#cvs.rfl' file to release the read lock. To obtain a writelock, first create the `#cvs.lock' directory, as with a readlock. Then check that there are no files whose names start with `#cvs.rfl.'. If there are, remove `#cvs.lock', wait for a while, and try again. If there are no readers, then create a file whose name is `#cvs.wfl' followed by information of your choice (for example, hostname and process identification number). Hang on to the `#cvs.lock' lock. Proceed with writing the repository. When you are done, first remove the `#cvs.wfl' file and then the `#cvs.lock' directory. Note that unlike the `#cvs.rfl' file, the `#cvs.wfl' file is just informational; it has no effect on the locking operation beyond what is provided by holding on to the `#cvs.lock' lock itself. Note that each lock (writelock or readlock) only locks a single directory in the repository, including `Attic' and `CVS' but not including subdirectories which represent other directories under version control. To lock an entire tree, you need to lock each directory (note that if you fail to obtain any lock you need, you must release the whole tree before waiting and trying again, to avoid deadlocks). Note also that CVS expects writelocks to control access to individual `foo,v' files. RCS has a scheme where the `,foo,' file serves as a lock, but CVS does not implement it and so taking out a CVS writelock is recommended. See the comments at rcs_internal_lockfile in the CVS source code for further discussion/rationale. File: cvs.info, Node: CVSROOT storage, Prev: Locks, Up: Repository storage How files are stored in the CVSROOT directory --------------------------------------------- The `$CVSROOT/CVSROOT' directory contains the various administrative files. In some ways this directory is just like any other directory in the repository; it contains RCS files whose names end in `,v', and many of the CVS commands operate on it the same way. However, there are a few differences. For each administrative file, in addition to the RCS file, there is also a checked out copy of the file. For example, there is an RCS file `loginfo,v' and a file `loginfo' which contains the latest revision contained in `loginfo,v'. When you check in an administrative file, CVS should print cvs commit: Rebuilding administrative file database and update the checked out copy in `$CVSROOT/CVSROOT'. If it does not, there is something wrong (*note BUGS::). To add your own files to the files to be updated in this fashion, you can add them to the `checkoutlist' administrative file (*note checkoutlist::). By default, the `modules' file behaves as described above. If the modules file is very large, storing it as a flat text file may make looking up modules slow (I'm not sure whether this is as much of a concern now as when CVS first evolved this feature; I haven't seen benchmarks). Therefore, by making appropriate edits to the CVS source code one can store the modules file in a database which implements the `ndbm' interface, such as Berkeley db or GDBM. If this option is in use, then the modules database will be stored in the files `modules.db', `modules.pag', and/or `modules.dir'. For information on the meaning of the various administrative files, see *Note Administrative files::. File: cvs.info, Node: Working directory storage, Next: Intro administrative files, Prev: Repository storage, Up: Repository How data is stored in the working directory =========================================== While we are discussing CVS internals which may become visible from time to time, we might as well talk about what CVS puts in the `CVS' directories in the working directories. As with the repository, CVS handles this information and one can usually access it via CVS commands. But in some cases it may be useful to look at it, and other programs, such as the `jCVS' graphical user interface or the `VC' package for emacs, may need to look at it. Such programs should follow the recommendations in this section if they hope to be able to work with other programs which use those files, including future versions of the programs just mentioned and the command-line CVS client. The `CVS' directory contains several files. Programs which are reading this directory should silently ignore files which are in the directory but which are not documented here, to allow for future expansion. The files are stored according to the text file convention for the system in question. This means that working directories are not portable between systems with differing conventions for storing text files. This is intentional, on the theory that the files being managed by CVS probably will not be portable between such systems either. `Root' This file contains the current CVS root, as described in *Note Specifying a repository::. `Repository' This file contains the directory within the repository which the current directory corresponds with. It can be either an absolute pathname or a relative pathname; CVS has had the ability to read either format since at least version 1.3 or so. The relative pathname is relative to the root, and is the more sensible approach, but the absolute pathname is quite common and implementations should accept either. For example, after the command cvs -d :local:/usr/local/cvsroot checkout yoyodyne/tc `Root' will contain :local:/usr/local/cvsroot and `Repository' will contain either /usr/local/cvsroot/yoyodyne/tc or yoyodyne/tc If the particular working directory does not correspond to a directory in the repository, then `Repository' should contain `CVSROOT/Emptydir'. `Entries' This file lists the files and directories in the working directory. The first character of each line indicates what sort of line it is. If the character is unrecognized, programs reading the file should silently skip that line, to allow for future expansion. If the first character is `/', then the format is: /NAME/REVISION/TIMESTAMP[+CONFLICT]/OPTIONS/TAGDATE where `[' and `]' are not part of the entry, but instead indicate that the `+' and conflict marker are optional. NAME is the name of the file within the directory. REVISION is the revision that the file in the working derives from, or `0' for an added file, or `-' followed by a revision for a removed file. TIMESTAMP is the timestamp of the file at the time that CVS created it; if the timestamp differs with the actual modification time of the file it means the file has been modified. It is stored in the format used by the ISO C asctime() function (for example, `Sun Apr 7 01:29:26 1996'). One may write a string which is not in that format, for example, `Result of merge', to indicate that the file should always be considered to be modified. This is not a special case; to see whether a file is modified a program should take the timestamp of the file and simply do a string compare with TIMESTAMP. If there was a conflict, CONFLICT can be set to the modification time of the file after the file has been written with conflict markers (*note Conflicts example::). Thus if CONFLICT is subsequently the same as the actual modification time of the file it means that the user has obviously not resolved the conflict. OPTIONS contains sticky options (for example `-kb' for a binary file). TAGDATE contains `T' followed by a tag name, or `D' for a date, followed by a sticky tag or date. Note that if TIMESTAMP contains a pair of timestamps separated by a space, rather than a single timestamp, you are dealing with a version of CVS earlier than CVS 1.5 (not documented here). The timezone on the timestamp in CVS/Entries (local or universal) should be the same as the operating system stores for the timestamp of the file itself. For example, on Unix the file's timestamp is in universal time (UT), so the timestamp in CVS/Entries should be too. On VMS, the file's timestamp is in local time, so CVS on VMS should use local time. This rule is so that files do not appear to be modified merely because the timezone changed (for example, to or from summer time). If the first character of a line in `Entries' is `D', then it indicates a subdirectory. `D' on a line all by itself indicates that the program which wrote the `Entries' file does record subdirectories (therefore, if there is such a line and no other lines beginning with `D', one knows there are no subdirectories). Otherwise, the line looks like: D/NAME/FILLER1/FILLER2/FILLER3/FILLER4 where NAME is the name of the subdirectory, and all the FILLER fields should be silently ignored, for future expansion. Programs which modify `Entries' files should preserve these fields. The lines in the `Entries' file can be in any order. `Entries.Log' This file does not record any information beyond that in `Entries', but it does provide a way to update the information without having to rewrite the entire `Entries' file, including the ability to preserve the information even if the program writing `Entries' and `Entries.Log' abruptly aborts. Programs which are reading the `Entries' file should also check for `Entries.Log'. If the latter exists, they should read `Entries' and then apply the changes mentioned in `Entries.Log'. After applying the changes, the recommended practice is to rewrite `Entries' and then delete `Entries.Log'. The format of a line in `Entries.Log' is a single character command followed by a space followed by a line in the format specified for a line in `Entries'. The single character command is `A' to indicate that the entry is being added, `R' to indicate that the entry is being removed, or any other character to indicate that the entire line in `Entries.Log' should be silently ignored (for future expansion). If the second character of the line in `Entries.Log' is not a space, then it was written by an older version of CVS (not documented here). Programs which are writing rather than reading can safely ignore `Entries.Log' if they so choose. `Entries.Backup' This is a temporary file. Recommended usage is to write a new entries file to `Entries.Backup', and then to rename it (atomically, where possible) to `Entries'. `Entries.Static' The only relevant thing about this file is whether it exists or not. If it exists, then it means that only part of a directory was gotten and CVS will not create additional files in that directory. To clear it, use the `update' command with the `-d' option, which will get the additional files and remove `Entries.Static'. `Tag' This file contains per-directory sticky tags or dates. The first character is `T' for a branch tag, `N' for a non-branch tag, or `D' for a date, or another character to mean the file should be silently ignored, for future expansion. This character is followed by the tag or date. Note that per-directory sticky tags or dates are used for things like applying to files which are newly added; they might not be the same as the sticky tags or dates on individual files. For general information on sticky tags and dates, see *Note Sticky tags::. `Checkin.prog' `Update.prog' These files store the programs specified by the `-i' and `-u' options in the modules file, respectively. `Notify' This file stores notifications (for example, for `edit' or `unedit') which have not yet been sent to the server. Its format is not yet documented here. `Notify.tmp' This file is to `Notify' as `Entries.Backup' is to `Entries'. That is, to write `Notify', first write the new contents to `Notify.tmp' and then (atomically where possible), rename it to `Notify'. `Base' If watches are in use, then an `edit' command stores the original copy of the file in the `Base' directory. This allows the `unedit' command to operate even if it is unable to communicate with the server. `Baserev' The file lists the revision for each of the files in the `Base' directory. The format is: BNAME/REV/EXPANSION where EXPANSION should be ignored, to allow for future expansion. `Baserev.tmp' This file is to `Baserev' as `Entries.Backup' is to `Entries'. That is, to write `Baserev', first write the new contents to `Baserev.tmp' and then (atomically where possible), rename it to `Baserev'. `Template' This file contains the template specified by the `rcsinfo' file (*note rcsinfo::). It is only used by the client; the non-client/server CVS consults `rcsinfo' directly.