Availability: Docs
Title: BuildGraph Script Anatomy
Crumbs: %ROOT%, Programming, Programming/Development, Programming/Development/BuildGraphs
Description:This page introduces you to our BuildGraph scripting system.
version: 4.13
parent:Programming/Development/BuildGraphs
type:Overview
tags:BuildGraph

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[TOC(start:1 end:4)]

If you want to learn how to write your own **BuildGraph** scripts, it helps to know the various parts that go into making a Graph. 
Graphs are created with the following elements:

* Tasks: Actions that are executed as part of a build process (compiling, cooking, etc.).
* Nodes: A named sequence of ordered tasks that are executed to produce outputs. Before they can be executed, nodes may depend 
on other nodes executing their tasks first.
* Agents: A group of nodes that are executed on the same machine (if running as part of a build system). Agents have no effect 
when building locally. 
* Triggers: Container for groups that should only be executed after manual intervention. 
* Aggregates: Groups of nodes and named outputs that can be referred to with a single name.

Scripts typically make frequent use of properties for reusable or conditionally defined values. Properties are declared with 
the `<Property>` element, and are scoped to the point of their first declaration. Properties referenced with the `$(Property 
Name)` notation are valid within all attribute strings, and will be expanded when the script is read. Properties that can be 
supplied by the user on the command-line can be declared with the `<Option>` element, and environment variables can be 
imported into properties using the `<EnvVar>` element.

Any element may be conditionally defined via the "If" attribute. See below for the syntax of conditional expressions.

BuildGraph is typically used for packaged games, so filtering and file manipulation are natively supported. Any attribute 
that accepts a list of files may consist of a Perforce style wildcard (matching any number of "...", "*" and "?" patterns in 
any location), a full path name, or a reference to a tagged collection of files. Attributes are denoted by prefixing a `#` 
character. Files may be added to a tag set using the `<Tag>` task, which also allows the performance of union/difference style 
operations. Each node can declare multiple outputs in the form of a list of named tags, which other nodes can then depend on.

Graphs may be executed in parallel as part of a build system. To do so, the initial graph configuration is generated by 
running with the `-Export=<Filename>` argument (producing a JSON file listing the nodes and dependencies to execute). Each 
participating agent should be synced to the same changelist, and AutomationTool (UAT) should be re-run with the appropriate 
`-SingleNode=<Name>` argument. Outputs from different nodes are transferred between agents via shared storage (typically, a 
network share) the path to which can be specified on the command line using the `-SharedStorageDir=<Path>` argument. Note that 
the allocation of machines (and coordination between them) is assumed to be managed by an external system.

The syntax of elements used to define BuildGraph constructs is listed in the following sections.

[INCLUDE:Programming/Development/BuildGraphs/BuildGraphTypes#buildgraphtypes]

[INCLUDE:Programming/Development/BuildGraphs/BuildGraphElements#buildgraphelements]

[INCLUDE:Programming/Development/BuildGraphs/BuildGraphConditions#buildgraphconditions]

[INCLUDE:Programming/Development/BuildGraphs/BuildGraphTasks#buildgraphtasks]