Cloud Files cURL Cookbook


The Rackspace Cloud Files service is offered with a RESTful API interface, which is useful for integration with existing into existing applications. At times, the interface can be used for directly interacting with the API to perform ad hoc tasks or to troubleshoot Cloud Files itself. A very useful tool for performing these actions from the command line is cURL, which is a generic client that supports several protocols, including HTTP. This article describes how to install cURL, its basic functions, and how to use it with Cloud Files.

Authenticating with the API

Cloud Files cURL Recipes

cURL installation

All the major distributions have packages for installing cURL. Following is an example of how to install cURL on Debian and Ubuntu:

$ sudo apt-get install curl

Similarly, the following command installs cURL on Fedora, CentOS, and Red Hat Enterprise Linux:

$ yum install curl

After cURL is installed, use the following command to verify that it is ready to use:

$ curl --version
curl 7.21.3 (i686-pc-linux-gnu) libcurl/7.21.3 OpenSSL/0.9.8o zlib/1.2.3.4 libidn/1.18
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smtp smtps telnet tftp
Features: GSS-Negotiate IDN IPv6 Largefile NTLM SSL libz

You can also install cURL on Microsoft Windows. To do so, visit the cURL homepage and download the executable from theDownloads page. The Windows binary will require installation of some Microsoft Visual C++ libraries to work correctly.

cURL basics

cURL is a command line tool that offers a means of communicating with various services at a protocol level. In particular, cURL supports HTTP(S) communication, which means that you can use it to query the HTTP-based API service endpoints and issue API operations with a fine level of detail.

This section provides some basic information about how to use cURL with HTTP.

Performing an HTTP GET

A HTTP GET operation is what browsers typically perform to download web pages and images whenever you go to a website. In the same manner, you can use cURL to issue an HTTP GET operation on a URL to get back the web page data.

Runing the following command with your favorite website URL returns the HTML markup.

$ curl http://www.example.com

By default, cURL sends the response body returned by the server directly to the terminal. You can also capture the output and send it directly to a file, which is effectively "downloading" the file or page. You can do this either by using the -o flag to specify an output file or by using the Linux redirection operator to capture the output, as shown in the following example:

$ curl -o index.html http://www.example.com
$ curl http://www.example.com > index.html

Performing an HTTP POST

You can also use cURL to perform an HTTP POST operation, which is what most HTML-based forms use to send data to a remote server. There are a few ways to tell cURL what data to send when doing a POST operation, but this article describes how to use the file-based method because many of the POST operations of the Rackspace Cloud API involve sending JSON or XML documents. To post an XML or JSON file, you need to specify the Content-Type appropriately so that the receiving server knows what to expect, as shown in the following examples:

$ curl -X POST -d @mydocument.xml -H "Content-Type: application/xml" http://www.example.com/form
$ curl -X POST -d @mydocument.json -H "Content-Type: application/json" http://www.example.com/form

You can also specify the data as a quoted string, but this can be unwieldy when done from the command line.

Performing an HTTP PUT

The HTTP PUT operation is similar to the HTTP POST operation, except PUT operations normally imply some sort of storage request. For example, uploading a object to a container is done using a PUT operation. When performing a PUT operation, it is important to specify the HTTP Content-Type header of the object that is being uploaded so that the receiving server knows what kind of file it is. cURL automatically passes through the required Content-Length headers to ensure that the file is uploaded in a standard fashion. The syntax is as follows:

$ curl -X PUT -T myobject.jpg -H "Content-Type: image/jpeg" http://www.example.com/upload

Viewing the HTTP headers

Many operations do not return a response body, just response headers. Much of the usefulness of the API result is in the headers, which contain useful information such as the HTTP response code. To view the HTTP response headers, use the -I option, as shown in the following example. This option is the equivalent of an HTTP HEAD request (X HEAD):

$ curl -I http://www.example.com
HTTP/1.0 302 Found
Location: http://www.iana.org/domains/example/
Server: BigIP
Connection: Keep-Alive
Content-Length: 0

Viewing More HTTP Debug Information

At times, it is useful to view the full HTTP request/response transaction. You can do this by using the verbose flag, which prints out practically all the HTTP data that is sent back and forth, including the request headers. This flag is quite useful for debugging purposes.

$ curl -v http://www.example.com
* About to connect() to www.example.com port 80 (#0)
* Trying 192.0.43.10... connected
* Connected to www.example.com (192.0.43.10) port 80 (#0)
> GET / HTTP/1.1
...

Sending HTTP Headers

When sending an HTTP request, it is sometimes useful to specify additional headers to give the server more information about the request you are making. A useful header to specify is the Accept header to indicate the type of response that you want back, either JSON or XML.

$ curl -v -H "Accept: application/xml" www.example.com
* About to connect() to www.example.com port 80 (#0)
* Trying 192.0.43.10... connected
* Connected to www.example.com (192.0.43.10) port 80 (#0)
> GET / HTTP/1.1 
> User-Agent: curl/7.21.3 (i686-pc-linux-gnu) libcurl/7.21.3 OpenSSL/0.9.8o zlib/1.2.3.4 libidn/1.18
> Host: www.example.com
> Accept: application/xml
>
...

Authenticating with the API

Before you can use any of the Rackspace Cloud APIs, you must first authenticate yourself to receive an authentication token. The token is an ID string that is required when you make calls to the various Rackspace Cloud APIs. The typical lifetime of a token is 24 hours, and you will always get the same token while it is still valid.

Note: Your token is crucial to your cloud service security, so keep it secret. If another user gets your token, that user might get full access to your cloud-based services.

To authenticate you need to query the Cloud Identity API. Version 1.1 of the Identity API sservice is used in the following example. To query the service, you need your Cloud username and API key. Instructions for locating these credentials are documented in Viewing and Regenerating Your API Key.

Authenticating requires sending a POST request to the Identity service with a document that contains your Cloud credentials. You can submit XML or JSON documents to the Rackspace Cloud APIs, but the remainder of the examples in this article will use XML documents because they are more descriptive. Following is an example XML document saved as auth.xml:

<?xml version="1.0" encoding="UTF-8"?>
<credentials xmlns="http://docs.rackspacecloud.com/auth/api/v1.1"
username="johndoe"
key="4e229b2e0789d9070e8411c9beee1c13"/>

After the XML document is ready, you can use cURL to send a POST request with the document to the API endpoint. The service endpoint that you use depends on whether you have a US-based or UK-based Cloud account:

  • US customers: https://auth.api.rackspacecloud.com/v1.1/auth
  • UK customers: https://lon.auth.api.rackspacecloud.com/v1.1/auth

The request will look like the following one for the user johndoe who is a US-based customer:

US customers: https://auth.api.rackspacecloud.com/v1.1/auth

UK customers: https://lon.auth.api.rackspacecloud.com/v1.1/auth

The curl based call will look like the following for johndoe who is a US based customer:

$ curl -X POST -d @auth.xml -H "Content-Type: application/xml" -H "Accept: application/xml" https://auth.api.rackspacecloud.com/v1.1/auth

The following examples shows the response to the authentication request:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<auth xmlns="http://docs.rackspacecloud.com/auth/api/v1.1">
<token expires="2012-01-17T03:52:09.000-06:00" id="3c5c8187-2569-47e0-8a11-edadd384e12b"/>
<serviceCatalog>
<service name="cloudFilesCDN">
<endpoint publicURL="https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b" v1Default="true" region="ORD"/>
</service>
<service name="cloudServers">
<endpoint publicURL="https://servers.api.rackspacecloud.com/v1.0/123456" v1Default="true"/>
</service>
<service name="cloudFiles">
<endpoint internalURL="https://snet-storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b" publicURL="https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b" v1Default="true" region="ORD"/>
</service>
</serviceCatalog>
</auth>

In the preceding response, note the following information that you will need when using the Cloud Files API:

  • API token
  • Cloud Files public endpoint URL
  • Cloud Files CDN (internal) endpoint URL

If your intend to access Cloud Files from a Cloud Server in the same data center, use the Cloud Files internal endpoint URL instead of the public one. Using this URL allows the API calls to go directly to the Cloud Files servers over the data center's ServiceNet private network. The benefit of using ServiceNet are that the Cloud Server does not incur bandwidth costs and the throughput rates to and from the Cloud Files storage servers are better.

Cloud Files cURL Recipes

This section contains cURL based recipes that you can use with Cloud Files API to quickly and easily do various Cloud Files related operations. The recipes are divided into two parts: storage operations and the CDN specific operations. To be able to make any of the following API calls, the authentication token needs to be passed along with the request. The following authentication token will be used in the below recipes: 3c5c8187-2569-47e0-8a11-edadd384e12b. We will also assume that we will be submitting and receiving only XML documents.

Storage Recipes

The storage recipes require the use of the Cloud Files service endpoint URL that was returned as part of the authentication process. The following recipes use the following example URL: https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b. When you use the recipes, be sure to substitute your own endpoint URL.

Listing Containers

Querying the Cloud Files storage endpoint returns a simple list of available containers, each on a new line.

$ curl -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/
backup
cloudservers
images
static

You can also list the containers with more details, including information such as the container, size and the number of objects within the container by passing the format parameter:

$ curl -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/?format=xml
<?xml version="1.0" encoding="UTF-8"?>
<account name="MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b">
<container>
<name>backup</name>
<count>1</count>
<bytes>54770176</bytes>
</container>
<container>
<name>cloudservers</name>
...

Creating a Container

Creating a container requires sending a PUT request to the storage URL and including a name for the container as part of the URL. The following example shows the request to create a new container called newcontainer:

$ curl -X PUT -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/newcontainer
202 Accepted

The request is accepted for processing.

Deleting a Container

You can delete a container by issuing a DELETE request, but remember that only empty containers can be deleted. If a container currently has objects within it, then those objects must first be deleted. No content body is returned as part of this request, so it is useful to also include the verbose flag to determine if the deletion was successful by verifying that an HTTP 204 response is returned.

$ curl -v -X DELETE -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/newcontainer
...
< HTTP/1.1 204 No Content
< Content-Length: 0
< Content-Type: text/html; charset=UTF-8
< X-Trans-Id: tx6eeb58f3dfa44f2e892505b711e8aefa
< Date: Wed, 01 Feb 2012 13:05:00 GMT

Listing Objects

Querying a container returns a simple list of objects within that container. By default only the first 10,000 objects are returned. The following example lists the objects of a container called images:

$ curl -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images
banner.jpg
cloud.png
rackspace.jpg

You can also use the format parameter to get more detailed information about objects, such as size and content type.

$ curl -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images?format=xml
<?xml version="1.0" encoding="UTF-8"?>
<container name="images">
<object>
<name>banner.jpg</name>
<hash>9ed61f72b1f3777ff01b7ce128a67244</hash>
<bytes>26326</bytes>
...

You can list more than 10,000 objects or to filter by specific objects by passing some additional URL parameter options. For more detailed information about the available parameters and how they work, see the Cloud Files Developer Guide.

Downloading an Object

Send a GET request on the full path to an object causes curl to effectively download the content. By default, the content goes straight to the terminal. It is possible to pipe the data printed to the terminal for processing or to simply redirect the data to a file to effectively save the contents. The following example downloads the cloud.png object from the images container to a local file of the same name by using the curl -o option to save the HTTP response body to a file:

$ curl -o cloud.png -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images/cloud.png

Uploading an Object

To upload a new object to a container, simply perform a PUT request of the file to be uploaded along with any additional options that you want such as file content-type headers. The following example uploads a file called style.css to a container called static with a content-type of text/css.

Note: Setting the correct content-type is important depending on where the object will be used. In the case of CSS files, for example, having an improper content type could cause web browsers to not parse the CSS when it served from the CDN, resulting in an unstyled web page.

$ curl -X PUT -T style.css -H "Content-Type: text/css" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/static/style.css
<html>
<head>
<title>201 Created</title>
</head>
<body>
<h1>201 Created</h1>
<br /><br />
</body>
</html>

You can also to upload an object to make it appear as if the object is part of a directory structure. You do this by naming the object with the full path including the directory components. This is useful when publishing containers to the CDN as the resulting CDN URL will appear as if it was part of a directory structure and is generally more organized. The following example repeats the preceding example but names the style.css object so that it becomes css/style.css:

$ curl -X PUT -T style.css -H "Content-Type: text/css" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/static/css/style.css
<html>
<head>
<title>201 Created</title>
</head>
<body>
<h1>201 Created</h1>
<br /><br />
</body>
</html>

Deleting an Object

To delete an object requires sending a DELETE request to the object to be deleted. It is useful to provide the verbose flag because the call does not return anything by default. An HTTP 204 No Content response code indicates a successful deletion.

$ curl -v -X DELETE -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/static/style.css ...
< HTTP/1.1 204 No Content
< Content-Length: 0
< Content-Type: text/html; charset=UTF-8
< X-Trans-Id: tx08e07264230f46cea4bdbaf998e301c0
< Date: Wed, 08 Feb 2012 19:24:17 GMT
<
* Connection #0 to host storage101.ord1.clouddrive.com left intact
* Closing connection #0 * SSLv3, TLS alert, Client hello (1):

Performing a Server Side Copy

To copy an existing object to a new storage location without incurring the expense of performing the data upload from the client side; particularly for very large files. By combining server-side copies with object deletion, you can perform object moves and rename operations by first copying the object to the new location or name and then performing a deletion of the original. Copying is not restricted to a single container. The following example copies the rackspace.jpg file to a new name of rackspace.jpeg as named in the Destination header:

$ curl -X COPY -H "Destination: images/rackspace.jpeg" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images/rackspace.jpg
<html>
<head>
<title>201 Created</title>
</head>
<body>
<h1>201 Created</h1>
<br /><br />
</body>
</html>

Updating Object Headers

You can update certain HTTP headers that correspond to an object by performing an HTTP POST operation to the object path with the updated header. This function is most useful for correcting an incorrectly set Content-Type header. Other headers that you can set include the CORS and Content-Disposition headers.

Note: You can also update the headers by performing a server-side copy and passing in the new header. To do this requires setting the destination of the copy to be the same as the source.

Following is an example of how to update the Content-Type of an image to image/jpeg by using the POST operation:

$ curl -X POST -H "Content-Type: image/jpeg" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://storage101.ord1.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images/rackspace.jpg
<html>
<head>
<title>202 Accepted</title>
</head>
<body>
<h1>202 Accepted</h1> The request is accepted for processing.<br /><br />
</body>
</html>

CDN Recipes

Cloud Files maintains a separate CDN API web service endpoint specifically for CDN-related operations. This URL is returned as part of the authentication process. The following recipes will use the following URL: https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b. When you use the recipes, be sure to substitute your own endpoint URL.

Listing CDN Enabled Containers

Performing a GET request on the CDN API URL returns a list of containers that have been CDN-enabled at some point. Containers that have never been CDN-enabled do not appear on this list. The following request lists all CDN-enabled containers:

$ curl -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12" https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b
files
static

CDN Enabling a Container

Before a container can have CDN operations performed on it, the container needs to be CDN enabled. You do this operation by performing a HTTP PUT to the CDN URL and naming the container in question. You can pass along additional CDN-related headers to initialize the content to certain CDN attributes such as container TTL and whether CDN logging should be enabled. If no additional CDN headers are passed along, the container is enabled with the default values.

Note: Making a container CDN enabled is not the same as publishing a container. CDN enabling container simply makes it CDN aware so that it can be used with the CDN. By default making a container CDN enabled also publishes it.

The following request enables and publishes the images container:

$ curl -X PUT -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12b" https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images
...
HTTP/1.1 204 No Content Date: Wed, 15 Feb 2012 20:28:29 GMT
Server: Apache
X-CDN-URI: http://c12345.r49.cf2.rackcdn.com
X-CDN-SSL-URI: https://c12345.ssl.cf2.rackcdn.com X-CDN-STREAMING-URI: http://c12345.r49.stream.cf2.rackcdn.com
X-CDN-Enabled: True
X-TTL: 259200
X-Log-Retention: False
Connection: close
Content-Type: text/plain; charset=UTF-8

Viewing a Container's CDN Details

To view a container's CDN properties requires sending an HTTP HEAD request to the API CDN URL. Viewable information includes whether the container is CDN enabled, if CDN logging is turned on, and the currently set TTL, as well as the various CDN domain names that can be used to reference content within the container.

The following request lists the CDN details of the images container:

$ curl -I -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12" https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images
HTTP/1.1 204 No
Content Date: Mon, 20 Feb 2012 19:39:41 GMT
Server: Apache
X-CDN-URI: http://c4965949.r49.cf2.rackcdn.com
X-CDN-SSL-URI: https://c4965949.ssl.cf2.rackcdn.com
X-CDN-STREAMING-URI: http://c4965949.r49.stream.cf2.rackcdn.com
X-CDN-Enabled: True
X-TTL: 259200
X-Log-Retention: False
Connection: close
Content-Type: text/plain; charset=UTF-8

Updating a Container's CDN Attributes

You can update the CDN attributes of a CDN-enabled container by sending an HTTP POST request to the API CDN URL naming the container to be updated and passing along one or more of the attribute headers. Trying to perform an update of a container that has never been CDN-enabled results in an HTTP 404 error. Because no response body is returned, use the verbose option to determine if the request was accepted.

Following is a list of CDN attributes that may be updated:

  • X-CDN-Enabled: indicates whether the container should be published or not, an unpublished container will not be publicly visible. Note that any existing content cached within the network will still be accessible using the CDN URL until the content's TTL expires and it is removed from the network. Accepts a value of True or False.
  • X-TTL: indicates the container's TTL value in seconds. This setting is applied to the container itself and all objects within and controls how long the content is cached within the CDN. It is not possible to have per object TTL values. There is a minimum limit of 15 minutes and a maximum limit of 50 years.
  • X-Log-Retention: indicates whether the container has CDN logging enabled. These are W3C style HTTP logs for all CDN content requests for the particular container. Accepts a value of True or False.

The following example request unpublishes a container called images:

$ curl -v -X POST -H "X-CDN-Enabled: False" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12" https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images ...
< HTTP/1.1 202 Accepted
< Date: Mon, 20 Feb 2012 19:33:33 GMT
< Server: Apache
< X-CDN-URI: http://c4965949.r49.cf2.rackcdn.com
< X-CDN-SSL-URI: https://c4965949.ssl.cf2.rackcdn.com
< X-CDN-STREAMING-URI: http://c4965949.r49.stream.cf2.rackcdn.com
< Content-Length: 0
< Connection: close
< Content-Type: text/plain; charset=UTF-8
<

Purging an Object

You can force the removal of content from the CDN by issuing a CDN purge request through an HTTP DELETE opreation to the content to be purged. The purge request can be done only on a per object basis. The purge request schedules a job with Akamai to have the indicated content removed from all member nodes of the CDN and can take some time to complete. You can pass through the X-Purge-Email header together with a comma-separated list of email addresses so that a notification will be sent when the purge is completed. Currently only 25 purges can be performed per account per day.

If you need to perform a container level purge, contact support via a ticket and name the container to be purged. Support can perform this purge for you. If a notification email is required,  also tell support the email addresses to use.

Note: Attempting to perform multiple purges on the same content while a previous purge is still running results in an HTTP 400 error.

The following operation performs a CDN purge of the rackspace.png file from the images container with a notification email set to user@example.com. (Use the verbose option because no response body is returned.)

$ curl -v -X DELETE -H "X-Purge-Email: user@example.com" -H "X-Auth-Token: 3c5c8187-2569-47e0-8a11-edadd384e12" https://cdn2.clouddrive.com/v1/MossoCloudFS_c4f83243-7537-4600-a94d-ab7065f0a27b/images/rackspace.png
...
>
< HTTP/1.1 204 No Content
< Date: Mon, 20 Feb 2012 20:10:18 GMT
< Server: Apache
< Content-Length: 0
< Connection: close
< Content-Type: text/plain; charset=UTF-8
<
* Closing connection #0
* SSLv3, TLS alert, Client hello (1):

Summary

This article is meant to serve as a quick reference to the more common Cloud Files API requests and how to use them with cURL. For more information about other features that the Cloud Files API offers, see the Cloud Files API documentation. The cURL techniques discussed in this article can also be used with other Rackspace Cloud based APIs and more generally for debugging HTTP and HTTPS based applications and web servers.



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