Notification

The develop_begin_command in the project configuration file (see aepconf(5) for more information) will be run, if specified. This is run after the aegis locks are released, so additional aegis commands may be run from here, if used with care. The symbolic links (see below) have not yet been created.

Development Directory Location

Please Note: Aegis also consults the underlying file system, to determine its notion of maximum file size. Where the file system's maximum file size is less than maximum_filename_length, the filesystem wins. This can happen, for example, when you are using the Linux UMSDOS file system, or when you have an NFS mounted an ancient V7 filesystem. Setting maximum_filename_length to 255 in these cases does not alter the fact that the underlying file systems limits are far smaller (12 and 14, respectively).

If your development directories (or your whole project) is on filesystems with filename limitations, or a portion of the heterogeneous builds take place in such an environment, it helps to tell Aegis what they are (using the project config file's fields) so that you don't run into the situation where the project builds on the more permissive environments, but fails with mysterious errors in the more limited environments.

If your development directories are routinely on a Linux UMSDOS filesystem, you would probably be better off setting dos_filename_required = true, and also changing the development_directory_template field. Heterogeneous development with various Windows environments may also require this.

Project Configuration

The development_directory_style field of the project configuration file controls the appearance of the development directory. See aepconf(5) for more information.

By using a setting such as

 
development_directory_style =
{
    source_file_symlink = true;
    during_build_only = true;
};

the user never sees the symbolic links, because they are added purely for the benefit of the dependency maintenance tool during the execution of the aeb(1) command.

By using a setting such as

 
development_directory_style =
{
    source_file_symlink = true;
};

(the other will default to false) the symbolic links will be created at develop begin time (see aedb(1) for more information) and also maintained by each aeb(1) invocation. Note that the symbolic links are only maintained at these times, so project integrations during the course of editing change sourec files may leave the symbolic links in an inconsistent state until the next build.

When files are copied from the baseline into a change, using the aecp(1) command, the symbolic link pointing into the baseline, if any, will be removed before the file is copied.

Note: Using this functionality in either form has implications for how the rules file of the dependency maintenance tool is written. Rules must remove their targets before creating them (usually with an rm -f command) if you use any of the link sub-fields (both hard links and symbolic links). This is to avoid attempting to write the result on the symbolic link, which will point at a read-only file in the project baseline. This is similar to the same requirement for using the link_integration_directory field of the project configuration file.

User Configuration

There is a symbolic_link_preference field in the user configuration file (see aeuconf(5) for more information). This controls whether aeb(1) will verify the symbolic links before the build (default) or whether it will assume they are up-to-date. (This field is only relevant if development_directory__style.source_file_symlink is true.)

For medium-to-large projects, verifying the symbolic links can take as long as the build itself. Assuming the symbolic links are up-to-date can be a large time-saving for these projects. It may be advisable to review your choice of DMT in such a situation.

The aedb(1) file does not consult this preference. Thus, in most situations, the symbolic links will be up-to-date when the build is performed. The only Aegis function which may result in the symbolic links becoming out-of-date is the integration of another change, as this may alter the presence or absence of files in the baseline. In this situation, the default aeb(1) action is to ignore the user preference and the verify symbolic links.

There are two command line options which modify aeb(1) behavior further: the -Verify-Symbolic-Links option says to verify the symbolic links; and the -Assume-Symbolic-Links option says to assume the symbolic links are up-to-date. In each case the option over-rides the default and the user preference.

It is possible to obtain behaviour similar to Tom Lord'a Arch by using a setting such as:

 
development_directory_style =
{
    source_file_link = true;
    source_file_symlink = true;
};

It is possible to obtain behaviour similar to CVS by using a setting such as:

 
development_directory_style =
{
    source_file_copy = true;
};

There are many more possible configurations of the development_directory_style, usually with helpful build side-effects. See aepconf(1) and the Depenedency Maintenance Tool chapter of the User Guide for more information.

The symbolic link command line options and preferences apply equally to hard links and file copies (the names have historical origins).