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communication functions

[%CFEngine_function_prototype(url, options_container)%]

Description: Retrieves the contents of a url using options from a data container. The data is returned in a data container.

NOTE that the options_container can be specified as inline JSON

[This function can accept many types of data parameters.][Functions#collecting functions]

Currently only file, http, and ftp URLs are supported. Internally, libcurl is used.

url_get() caches its results. To invalidate the cache, use a different set of options, e.g. by modifying an unused key with the system time.

If the libcurl integration is not available, the function will exit with an error and the variable will remain undefined. If the libcurl initialization fails, the function will also exit with an error. In every other normal case, the function will return a valid data container. In official CFEngine packages, libcurl integration is always provided.

The available options currently are:

  • url.max_content: if present, specifies the maximum number of content bytes to retrieve.
  • url.max_headers: if present, specifies the maximum number of response headers to retrieve.
  • url.verbose: if 1, libcurl will be more verbose while retrieving the content
  • url.timeout: if present, libcurl will time out the request after that many seconds
  • url.referer: if present, libcurl will set the Referer to this
  • url.user-agent: if present, libcurl will set the User-Agent to this
  • url.headers: an array of strings in the format Foo: bar specifying headers for the request

The returned data container will have the following keys:

  • returncode: the HTTP response code, e.g. 200.
  • rc: the libcurl integer result code, either 0 for success or something else for failure
  • error_message: when present, indicates the request was unsuccessful and explains why
  • success: a boolean. When success is false, the result code was not 0 and the request was unsuccessful.
  • content: the response content as a string
  • headers: the response headers as a string

[%CFEngine_function_attributes(url, options_container)%]


This example retrieves two URLs using one set of options. The options are specified in JSON and parsed into a data container options. That data container is then passed to each invocation of url_get.

bundle agent main
      "options_str" string => '
  "url.max_content": 512,
  "url.verbose": 0,
  "url.headers": [ "Foo: bar" ]
      "options" data => parsejson($(options_str));
      "url" string => "";
      "res" data => url_get($(url), options);
      "out" string => format("%S", res);

      "url2" string => "";
      "res2" data => url_get($(url2), options);
      "out2" string => format("%S", res2);

      "$(this.bundle): from $(url) with options $(options_str) we got $(out)";
      "$(this.bundle): from $(url2) with options $(options_str) we got $(out2)";


R: main: from with options
  "cfengine.max_content": 512,
  "curl.verbose": 0,
  "curl.headers": [ "Foo: bar" ]
} we got {"returncode":200,"rc":0,"success":true,"content":"\n<!DOCTYPE html>\n<!--[if lt IE 7]>\n<html class=\"no-js lt-ie9 lt-ie8 lt-ie7\" lang=\"en-US\" prefix=\"og:\"> <![endif]-->\n<!--[if IE 7]>\n<html class=\"no-js lt-ie9 lt-ie8\" lang=\"en-US\" prefix=\"og:\"> <![endif]-->\n<!--[if IE 8]>\n<html class=\"no-js lt-ie9\" lang=\"en-US\" prefix=\"og:\"> <![endif]-->\n<!--[if gt IE 8]><!-->\n<html class=\"no-js\" lang=\"en-US\" prefix=\"og:\"> <!--<![endif]-->\n<head>\n\n    \n    <meta charset=\"utf-8\">\n\n    <title>\n        CFEng","headers":"HTTP/1.1 200 OK\r\nDate: Fri, 27 Mar 2015 18:13:01 GMT\r\nServer: Apache\r\nX-Powered-By: PHP/5.3.3\r\nX-Pingback:\r\nConnection: close\r\nTransfer-Encoding: chunked\r\nContent-Type: text/html; charset=UTF-8\r\n\r\n"}

R: main: from with options
  "cfengine.max_content": 512,
  "curl.verbose": 0,
  "curl.headers": [ "Foo: bar" ]
} we got {"returncode":0,"rc":6,"success":false,"content":"","headers":""}

History: Introduced in CFEngine 3.8. The [collecting function][Functions#collecting functions] behavior was added in 3.9.

See also: readtcp(), mergedata(), parsejson(), [about collecting functions][Functions#collecting functions], and data documentation.

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