Provides a pattern or expression specifying files or directories that should be included alongside the primary file. If the value is an expression, the value of self in the expression must be the primary input or output File object to which this binding applies. The basename, nameroot and nameext fields must be present in self. For CommandLineTool outputs the path field must also be present. The expression must return a filename string relative to the path to the primary File, a File or Directory object with either path or location and basename fields set, or an array consisting of strings or File or Directory objects. It is legal to reference an unchanged File or Directory object taken from input as a secondaryFile. The expression may return "null" in which case there is no secondaryFile from that expression. To work on non-filename-preserving storage systems, portable tool descriptions should avoid constructing new values from location, but should construct relative references using basename or nameroot instead. If a value in secondaryFiles is a string that is not an expression, it specifies that the following pattern should be applied to the path of the primary file to yield a filename relative to the primary File: 1. If string ends with ? character, remove the last ? and mark the resulting secondary file as optional. 2. If string begins with one or more caret ^ characters, for each caret, remove the last file extension from the path (the last period . and all following characters). If there are no file extensions, the path is unchanged. 3. Append the remainder of the string to the end of the file path.
An implementation must not fail workflow execution if required is set to false and the expected secondary file does not exist. Default value for required field is true for secondary files on input and false for secondary files on output.