Table of Contents

mergedata

Table of Contents

Prototype: mergedata(one, two, etc)

Return type: data

Description: Returns the merger of any named data containers or lists.

The returned data container will have the keys from each of the named data containers.

If all data containers are JSON arrays, they are merged into a single array, as you'd expect from merging two arrays.

If any of the data containers are JSON objects, all the containers are treated as JSON objects (for arrays, the key is the element's offset).

If any list (slist, ilist, or rlist) is named, it's first converted to a JSON array, then merged as above.

If any CFEngine "classic" array (array[key]) is named, it's first converted to a JSON object, then merged as above.

mergedata() is thus a convenient way, together with getindices() and getvalues(), to bridge the gap between data container and the traditional list and array data types in CFEngine.

Example:

body common control
{
      bundlesequence => { "test", "test2" };
}

bundle agent test
{
  vars:
      "d1" data => parsejson('{ "a": [1,2,3], "b": [] }');
      "d2" data => parsejson('{ "b": [4,5,6] }');
      "d3" data => parsejson('[4,5,6]');
      "list1" slist => { "element1", "element2" };
      "array1[mykey]" slist => { "array_element1", "array_element2" };
      "array2[otherkey]" string => "hello";

      "merged_d1_d2" data => mergedata("d1", "d2");
      "merged_d1_d3" data => mergedata("d1", "d3");
      "merged_d3_list1" data => mergedata("d3", "list1");

      "merged_d1_array1" data => mergedata("d1", "array1");
      "merged_d2_array2" data => mergedata("d2", "array2");

      "merged_d1_d2_str" string => format("merging %S with %S produced %S", d1, d2, merged_d1_d2);
      "merged_d1_d3_str" string => format("merging %S with %S produced %S", d1, d3, merged_d1_d3);
      "merged_d3_list1_str" string => format("merging %S with %S produced %S", d3, list1, merged_d3_list1);

      "merged_d1_array1_str" string => format("merging %S with %s produced %S", d1, array1, merged_d1_array1);
      "merged_d2_array2_str" string => format("merging %S with %s produced %S", d2, array2, merged_d2_array2);
  reports:
      "$(merged_d1_d2_str)";
      "$(merged_d1_d3_str)";
      "$(merged_d3_list1_str)";
      "$(merged_d1_array1_str)";
      "$(merged_d2_array2_str)";
}

bundle agent test2
{
  vars:
      "a"       data  => parsejson('{ "a": "1" }'), meta => { "mymerge" };
      "b"       data  => parsejson('{ "b": "2" }'), meta => { "mymerge" };
      "c"       data  => parsejson('{ "c": "3" }'), meta => { "mymerge" };
      "d"       data  => parsejson('{ "d": "4" }'), meta => { "mymerge" };
      "todo"    slist => variablesmatching(".*", "mymerge");

  methods:
      "go" usebundle => cmerge(@(todo)); # a, b, c, d

  reports:
      "$(this.bundle): merged containers with cmerge = $(cmerge.all_str)";
}

bundle agent cmerge(varlist)
{
  vars:
      "all"     data => parsejson('[]'),            policy => "free";
      "all"     data => mergedata(all, $(varlist)), policy => "free";
      "all_str" string => format("%S", all),        policy => "free";
}

Output:

R: merging {"a":[1,2,3],"b":[]} with {"b":[4,5,6]} produced {"a":[1,2,3],"b":[4,5,6]}
R: merging {"a":[1,2,3],"b":[]} with [4,5,6] produced {"a":[1,2,3],"b":[],"0":4,"1":5,"2":6}
R: merging [4,5,6] with { "element1", "element2" } produced [4,5,6,"element1","element2"]
R: merging {"a":[1,2,3],"b":[]} with array1 produced {"a":[1,2,3],"b":[],"mykey":["array_element1","array_element2"]}
R: merging {"b":[4,5,6]} with array2 produced {"b":[4,5,6],"otherkey":"hello"}
R: test2: merged containers with cmerge = {"a":"1","b":"2","c":"3","d":"4"}

See also: getindices(), getvalues(), readjson(), parsejson(), and data documentation.