write_objects

File write_objects(Array[Struct|Object])

Writes a tab-separated value (TSV) file with the contents of a Array[Struct] or Array[Object]. All elements of the Array must have the same member names, or an error is raised.

The file contains N+1 tab-delimited lines, where N is the number of elements in the Array. The first line is the names of the Struct/Object members, and the subsequent lines are the corresponding values for each element. Each line is terminated by a newline (\n) character. The lines are written in the same order as the elements in the Array. The ordering of the columns is the same as the order in which the Struct's members are defined; the column ordering for Objects is unspecified. If the Array is empty, an empty file is written.

The member values must be serializable to strings, meaning that only primitive types are supported. Attempting to write a Struct or Object that has a compound member value results in an error.

Parameters

1. Array[Struct|Object]: An array of objects to write.

Returns: A File.

Example: write_objects_task.wdl

version 1.2

task write_objects {
  input {
    Array[Object] obj_array
  }

  command <<<
    cut -f 1 ~{write_objects(obj_array)}
  >>>
  
  output {
    Array[String] results = read_lines(stdout())
  }
}

{
  "write_objects.obj_array": [
    {
      "key_1": "value_1",
      "key_2": "value_2",
      "key_3": "value_3"
    },
    {
      "key_1": "value_4",
      "key_2": "value_5",
      "key_3": "value_6"
    },
    {
      "key_1": "value_7",
      "key_2": "value_8",
      "key_3": "value_9"
    }
  ]
}

{
  "write_objects.results": ["key_1", "value_1", "value_4", "value_7"]
}

The actual command line might look like:

cut -f 1 /path/to/input.tsv

If obj_array has the items:

The /path/to/input.tsv will contain:

key_1\tkey_2\tkey_3
value_1\tvalue_2\tvalue_3
value_4\tvalue_5\tvalue_6
value_7\tvalue_8\tvalue_9