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# History browsing

Once you have used CVS to store a version control history--what files have changed when, how, and by whom, there are a variety of mechanisms for looking through the history.

- log messages: Log messages
- history database: The history database
- user-defined logging: User-defined logging
- annotate: What revision modified each line of a file?

## Log messages

Whenever you commit a file you specify a log message.

To look through the log messages which have been specified for every revision which has been committed, use the `cvs log` command (see section log--Print out log information for files).

## The history database

You can use the history file (see section The history file) to log various CVS actions. To retrieve the information from the history file, use the `cvs history` command (see section history--Show status of files and users).

## User-defined logging

You can customize CVS to log various kinds of actions, in whatever manner you choose. These mechanisms operate by executing a script at various times. The script might append a message to a file listing the information and the programmer who created it, or send mail to a group of developers, or, perhaps, post a message to a particular newsgroup. To log commits, use the ``loginfo'` file (see section Loginfo). To log commits, checkouts, exports, and tags, respectively, you can also use the ``-i'`, ``-o'`, ``-e'`, and ``-t'` options in the modules file. For a more flexible way of giving notifications to various users, which requires less in the way of keeping centralized scripts up to date, use the `cvs watch add` command (see section Telling CVS to notify you); this command is useful even if you are not using `cvs watch on`.

The ``taginfo'` file defines programs to execute when someone executes a `tag` or `rtag` command. The ``taginfo'` file has the standard form for administrative files (see section Reference manual for Administrative files), where each line is a regular expression followed by a command to execute. The arguments passed to the command are, in order, the tagname, operation (`add` for `tag`, `mov` for `tag -F`, and `del` for `tag -d`), repository, and any remaining are pairs of filename revision. A non-zero exit of the filter program will cause the tag to be aborted.

Here is an example of using taginfo to log tag and rtag commands. In the taginfo file put:

    ALL /usr/local/cvsroot/CVSROOT/loggit

Where ``/usr/local/cvsroot/CVSROOT/loggit'` contains the following script:

    #!/bin/sh
    echo "$@" >>/home/kingdon/cvsroot/CVSROOT/taglog

## Annotate command

Command: cvs annotate [`-flR`] [`-r rev`|`-D date`] files ...

  For each file in files, print the head revision of the trunk, together with information on the last modification for each line. For example:

      $ cvs annotate ssfile
      Annotations for ssfile
      ***************
      1.1          (mary     27-Mar-96): ssfile line 1
      1.2          (joe      28-Mar-96): ssfile line 2

  The file ``ssfile'` currently contains two lines. The `ssfile line 1` line was checked in by `mary` on March 27. Then, on March 28, `joe` added a line `ssfile line 2`, without modifying the `ssfile line 1` line. This report doesn't tell you anything about lines which have been deleted or replaced; you need to use `cvs diff` for that (see section diff--Show differences between revisions).

The options to `cvs annotate` are listed in section Quick reference to CVS commands, and can be used to select the files and revisions to annotate. The options are described in more detail in section Common command options.

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