targets.rst

Targets

As a build system, Rabs works on targets. A target is anything that can be built or changed, both by the build and externally. Each time Rabs is run, it takes the necessary actions to ensure a particular target is up to date. This may involve checking other targets, and rebuilding them as necessary.

Every target has the following attributes:

A unique identifier

Every target has a unique identifer. Likewise, every identifier corresponds to a unique target. This allows targets to be referenced across multiple scripts within a build.

Some examples of identifiers:

• file("test.c") has identifier "file:test.c".
• meta("NAME") has identifier :samp:`"meta:{context path}:NAME"` where context path is the path of the enclosing context.

An optional build function

A target can have a build function which is called whenever the target needs to be rebuilt, or if the target is missing. To set the build function for a target, use the => operator:

Optional dependencies

A target can depend on other targets. If any dependency of a target is changed during a build then the target itself will be rebuilt (assuming it has a build function) and rechecked. To add dependencies to a target, use the [] operator. Both individual dependencies and lists of dependencies are accepted.

A SHA-256 checksum

Every target has a checksum created once the target is built. If the target is rebuilt, or possibly changed externally, a new checksum is calculated and compared to the previous one. If the checksum has changed, then the target is considered updated.

Methods

Every target supports the following methods:

Target => BuildFunction

Sets the build function for Target to BuildFunction.

Target[Dependency, Dependency, ...]

Adds dependencies to Target. Each dependency can itself be a list of further dependencies, in case the list of dependencies is generated by code.

Target:scan(Name)

Creates a scan target called Name associated with Target. See :doc:`/targets/scans` for more details.

Some target types provide other methods, these are documented in the respective sections.

Target Types

.. toctree::
   :maxdepth: 2

   /targets/expressions
   /targets/files
   /targets/meta
   /targets/scans
   /targets/symbols