Added lines for sections on wget, lftp, and curl

novice/extras/10-file_transfer.md

@@ -4,21 +4,20 @@ root: ../..
 title: File Transfer
 ---
 There are other ways to interact with remote files other than git.
-In fact, if we wish to download files from the shell we can use
-Wget, cURL, and ftp.
+
+It is true that we can clone an entire git repository, or even one level of a git repository using: git clone --depth-1 repository_name.
+What about files that do not exist in a git repository? If we wish to download files from the shell we can use tools such as
+Wget, cURL, and lftp.
 
 #### Wget
 
 Wget is a simple tool developed for the GNU Project that downloads files with the HTTP, HTTPS and FTP protocols. It is widely used by unix users and is available with most Linux distributions.
 
-To download this lesson from the web via http with the URL http://software-carpentry.org/v5/novice/extras/10-file_transfer.html we can simply type:
-
+To download this lesson (located at http://software-carpentry.org/v5/novice/extras/10-file_transfer.html) from the web via HTTP we can simply type:
 ~~~
 $ wget http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
 ~~~
 {:class="in"}
-
-To produce output similar to:
 ~~~
 --2014-11-21 09:41:31--  http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
 Resolving software-carpentry.org (software-carpentry.org)... 174.136.14.108
@@ -33,11 +32,57 @@ Saving to: `10-file_transfer.html'
 ~~~
 {:class="out"}
 
+Alternatively, you can add more options, which are in the form:
+
+~~~
+wget -r -np -D domain_name target_URL
+~~~
+{:class="in"}
+
+where "-r" means recursively crawl to other files and directories, "-np" means avoid crawling to parent directories, "-D" means to target only the following domain name
+
+For our URL it would be:
+~~~
+$ wget -r -np -D software-carpentry.org http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
+~~~
+{:class="in"}
+
+To restrict retrieval to a particular extension(s) we can use the -A option followed by a comma separated list:
+~~~
+wget -r -np -D software-carpentry.org -A html http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
+~~~
+{:class="in"}
+
+We can also clone a webpage with its local dependencies:
+~~~
+$ wget -mkq target_URL
+~~~
+
+We could also clone the entire website:
+~~~
+$ wget -mkq -np -D domain_name domain_name_URL
+~~~
+and add the "-nH" option if we do not want a subdirectory created for the websites content:
+
+e.g.
+~~~
+$ wget -mkq -np -nH -D example.com http://example.com
+~~~
+
+where:
+-m is for mirroring with time stamping, infinite recursion depth, and preservation of FTP directory settings
+-k converts links to make them suitable for local viewing 
+-q supresses the output to the screen
+
+The above command can also save the clone the contents of one domain to another if we are using ssh or sshfs to access a webserver. 
+
+Please refer to the man page by typing "man wget" in the shell for more information.
+
 ### cURL
 
-Alternatively, we can use cURL. It supports a much larger range of protocolsincluding common mail based protocols like pop3 and smtp. 
+Alternatively, we can use cURL. It supports a much larger range of protocols including common mail based protocols like pop3 and smtp. 
 
-Functionally equivalent behaviour to the wget http request above may be invoked by typing:
+To download this lesson (located at http://software-carpentry.org/v5/novice/extras/10-file_transfer.html) from the web via HTTP we can simply type:
 
 ~~~
 $ curl -o 10-file_transfer.html http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
@@ -51,30 +96,61 @@ To produce output similar to:
 ~~~
 {:class="out"}
 
-### lftp
+This input to curl is in the form:
+curl -o filename_for_local_machine target_url
 
-Another option is lftp. It has a lot of capability, and even does simple bitorrent. 
+where the "-o" option says write the output to a file instead of the stdout (the screen), and file_name_for_local_machine is any file name you choose to save to the local machine, and target_URL is where the file is the URL where the file is on the web
 
-~~~~
-$ lftp -c get 03-review.html http://software-carpentry.org/v5/novice/extras/03-review.html
+Removing the -o option, and following the syntax "curl target_URL" outputs the contents of the url to the screen. If we wanted to enhance the functionality we have we could use information from the pipes and filters section, which is lesson 4 from the unix shell session.
+For example, we could type "curl http://software-carpentry.org/v5/novice/extras/10-file_transfer.html
+ | grep curl" which would tell us that indeed this URL contains the string curl. We could make the output cleaner by limiting the output of curl to just the file contents by using the "-s" option
+(e.g. curl -s http://software-carpentry.org/v5/novice/extras/10-file_transfer.html | grep curl). 
+
+If we wanted only the text and not the html tags in our output we could use html to text parser such as html2text.
+~~~
+$ curl -s http://software-carpentry.org/v5/novice/extras/10-file_transfer.html | html2text | grep curl
 ~~~
-(:class="in"}
+{:class="in"}
+
+With wget, we can obtain the same results by typing:
 ~~~
-get: Not connected
+$ wget -q -D software-carpentry.org -O /dev/stdout http://software-carpentry.org/v5/novice/extras/10-file_transfer.html | html2text | grep curl
 ~~~
-(:class="out"}
+{:class="in"}
+
+Wget offers more functionality natively than curl for retrieving entire directories. We could use Wget to first retrieve an entire directory and then run html2text and grep to find a particular string. cURL is limited to retrieving one or more specified URLs that cannot be obtained by recursively crawling a directory. The situation may be improved by combining with other unix tools, but is not thought as being as good as Wget.
 
-Please refer to the man page to experiment with other protocols, such as FTP (e.g. man wget, man curl, man lftp).
+Please refer to the man pages by typing "man wget", "man curl", and "man html2text" in the shell for more information. 
 
-Sources:
+### lftp
 
-Wget - Wikipedia, http://en.wikipedia.org/wiki/Wget, Accessed: 11/21/2011
+Another option is lftp. It has a lot of capability, and even does simple bitorrent. 
 
-cURL - Wikipedia, http://en.wikipedia.org/wiki/CURL, Accessed: 11/21/2011
+If we want to retrieve 03-review.html on the website and save it with the filename 03-review.html locally:
+~~~
+$ lftp -c get http://software-carpentry.org/v5/novice/extras/03-review.html
+~~~
+{:class="in"}
+
+If we want to print 03-review.html to the screen instead:
+~~~
+$ lftp -c cat http://software-carpentry.org/v5/novice/extras/03-review.html
+~~~
+{:class="in"}
+
+To obtain retrive all of the files with a particular extension in a directory we can type:
+~~~
+$ lftp -c mget {URL for directory}/*.extension_name
+~~~
+{:class="in"}
+
+For example, to retrieve all of the .html files in the extras folder:
+~~~
+$ lftp -c mget http://software-carpentry.org/v5/novice/extras/*.html
+~~~
 
-lftp - Wikipedia, http://en.wikipedia.org/wiki/Lftp, Accessed: 11/21/2011
+Please refer to the man page by typing "man lftp" in the shell for more information.
 
-lftp man page, Accessed: 11/21/2011