Monday, 6 July 2015

Connections : Interfaces to the outside world

Data can be read/write to external world using connection interfaces, By using connection interface, you can read/write data from/to a file, url etc.,

file : Opens connection to a file
gzfile : Opens connection to a file compressed with gzip
bzfile : Opens connection to a file compressed with bzip2
xzfile : Opens connection to a file compressed with xz
url : Opens connection to a webpage

Read data from URL
url.show("https://self-learning-java-tutorial.blogspot.com")
Above statement download content from given url and display the data in separate window.

> url.show("https://self-learning-java-tutorial.blogspot.com")
trying URL 'https://self-learning-java-tutorial.blogspot.com'
Content type 'text/html; charset=UTF-8' length unknown
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
.......... .......... .......... .......... ..........
..
downloaded 252 KB


Another way to read from URL

> con <- url("https://self-learning-java-tutorial.blogspot.com", "r")
>
> x <- readLines(con)
Warning message:
>
> head(x)
[1] "<!DOCTYPE html>"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
[2] "<html class='v2' dir='ltr' xmlns='http://www.w3.org/1999/xhtml' xmlns:b='http://www.google.com/2005/gml/b' xmlns:data='http://www.google.com/2005/gml/data' xmlns:expr='http://www.google.com/2005/gml/expr'>"                                                                                                                                                                                                                                                                                                                                                                                                                            
[3] "<head>"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
[4] "<meta content='width=1100' name='viewport'/>"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
[5] "<meta content='text/html; charset=UTF-8' http-equiv='Content-Type'/>"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
[6] "<script type=\"text/javascript\">(function() { var b=window,f=\"chrome\",g=\"tick\",k=\"jstiming\";(function(){function d(a){this.t={};this.tick=function(a,d,c){var e=void 0!=c?c:(new Date).getTime();this.t[a]=[e,d];if(void 0==c)try{b.console.timeStamp(\"CSI/\"+a)}catch(h){}};this[g](\"start\",null,a)}var a;b.performance&&(a=b.performance.timing);var n=a?new d(a.responseStart):new d;b.jstiming={Timer:d,load:n};if(a){var c=a.navigationStart,h=a.responseStart;0<c&&h>=c&&(b[k].srt=h-c)}if(a){var e=b[k].load;0<c&&h>=c&&(e[g](\"_wtsrt\",void 0,c),e[g](\"wtsrt_\",\"_wtsrt\",h),e[g](\"tbsd_\",\"wtsrt_\"))}try{a=null,"



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