The step returns a c:result element with attributes describing properties of the system. It must include the following properties. The attribute can be an empty string if they do not apply to the runtime environment. For example cwd will be an empty string on systems which have no concept of a working directory the value of the attribute will be empty.
file-separator
The file separator; usually "/" on Unix, "\" on Windows.
path-separator
The path separator; usually ":" on Unix, ";" on Windows.
os-architecture
The operating system architecture, for example "i386".
os-name
The name of the operating system, for example "Mac OS X".
os-version
The version of the operating system, for example "10.5.6".
cwd
The current working directory.
user-name
The login name of the effective user, for example "ndw".
user-home
The home directory of the effective user, for example "/home/ndw".
The c:result element can contain zero or more c:environment elements that identify the environment variables available. These elements have a mandatory name and value attribute, reflecting name and value of the environment variable. Implementations should include all available operating system environment variables.
The exact set of properties returned is implementation-defined. Additional attributes must be in a namespace.
Document properties
The resulting document has no properties apart from content-type. In particular, it has no base-uri.
2.2. p:os-exec
The p:os-exec step runs an external command passing the input that arrives on its source port as standard input, reading result from standard output, and error from standard error.
The p:os-exec step executes the command passed on command with the arguments passed on args. The processor does not interpolate the values of the command or args (for example, expanding references to environment variables). It is a dynamic error (err:XC0033) if the command cannot be run.
If the cwd option is specified, it identifies the directory that will be the current working directory when execution begins. To resolve variations in the syntax of directory specifications (“/tmp” vs. “C:\tmp” vs “file:///c:/tmp”, for example), the value will be normalized with the p:urify function. It is a dynamic error (err:XC0034) if the current working directory cannot be changed to the value of the cwd option. If cwd is not specified, the current working directory is implementation-defined.
If the path-separator option is specified, every occurrence of the character identified as the path-separator character that occurs in the command, args, or cwd will be replaced by the platform-specific path separator character. It is a dynamic error (err:XC0063) if the path-separator option is specified and is not exactly one character long.
The source port is declared to accept a sequence so that it can be empty. If no document appears on the source port, then the command receives nothing on standard input. If a document does arrive on the source port, it will be passed to the command as its standard input. It is a dynamic error (err:XC0032) if more than one document appears on the source port of the p:os-exec step. The serialization option is used to control the serialization of the document before passing it to the standard input. If a document has a “serialization” document property, the effective value of the serialization options is the union of the two maps, where the entries in the “serialization” document property take precedence. Serialization is described in XProc 3.1.
If there is content on standard output, it is read and processed as described in p:load with result-content-type taken as value for p:load's content-type option. The created document is returned on result. Otherwise result will be empty.
If there is content on standard error, it is read and processed as described in p:load with error-content-type taken as value for p:load's content-type option. The created document is returned on error. Otherwise error will be empty.
The exit-status port always returns a single c:result element which contains the system exit status that the process returned. The specific exit status values returned by a process invoked with p:os-exec are implementation-dependent.
If a failure-threshold value is supplied, and the exit status is greater than that threshold, then the p:os-exec step must fail. It is a dynamic error (err:XC0064) if the exit code from the command is greater than the specified failure-threshold value. This failure, like any step failure, can be captured with a p:try.
A dynamic error is one which occurs while a pipeline is being evaluated. Examples of dynamic errors include references to URIs that cannot be resolved, steps which fail, and pipelines that exhaust the capacity of an implementation (such as memory or disk space). For a more complete discussion of dynamic errors, see Dynamic Errors in XProc 3.1: An XML Pipeline Language.
If a step fails due to a dynamic error, failure propagates upwards until either a p:try is encountered or the entire pipeline fails. In other words, outside of a p:try, step failure causes the entire pipeline to fail.
The following errors can be raised by these steps:
Step Errors
err:XC0032
It is a dynamic error if more than one document appears on the source port of the p:os-exec step.
An implementation-dependent feature is one where the implementation has discretion in how it is performed. Implementations are not required to document or explain how implementation-dependent features are performed.
An implementation-defined feature is one where the implementation has discretion in how it is performed. Conformant implementations must document how implementation-defined features are performed.
1. Implementation-defined features
The following features are implementation-defined:
An implementation-defined feature is one where the implementation has discretion in how it is performed. Conformant implementations must document how implementation-defined features are performed.
An implementation-dependent feature is one where the implementation has discretion in how it is performed. Implementations are not required to document or explain how implementation-dependent features are performed.
Appendix D. Ancillary files
This specification includes by reference a number of ancillary files.