Clojure language 7: I/O

Corresponding to stdin, stdout, and stderr, clojure provide three symbols by default: * In *, * out *, and * err.

You can use the binding macro to perform redirection. For example, the following example redirects * out * to a file:

user=> (binding [*out* (java.io.FileWriter. "/home/chenshu/tt")] (println "Write to tt.") (flush))nil

Statements originally output to the console are now written to the TT file. Note that (flush) is used to write data in the buffer to * out.

This redirection is only valid in the binding expression. After leaving this expression, * out * is still stdout.

You can directly read the file and use the slurp function ):

user=> (slurp "/home/chenshu/a.xml")"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<service>\n  <mongodb>\n    <uri>localhost</uri>\n  </mongodb>\n  <socket>\n    <port_number>7777</port_number>    \n    <login_timeout>200</login_timeout>\n    <check_timeout>200</check_timeout>\n  </socket>\n</service>\n"

Write a program to read the configuration file and save the content to VaR for future use:

user=> (def s (slurp "/home/chenshu/a.xml"))#'user/suser=> s"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<service>\n  <mongodb>\n    <uri>localhost</uri>\n  </mongodb>\n  <socket>\n    <port_number>7777</port_number>    \n    <login_timeout>200</login_timeout>\n    <check_timeout>200</check_timeout>\n  </socket>\n</service>\n"

The above redirection is not required. You can use the following function spit to write files:

user=> (spit "b.xml" s)niluser=> (slurp "b.xml")"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<service>\n  <mongodb>\n    <uri>localhost</uri>\n  </mongodb>\n  <socket>\n    <port_number>7777</port_number>    \n    <login_timeout>200</login_timeout>\n    <check_timeout>200</check_timeout>\n  </socket>\n</service>\n"user=> 

The clojure language is also evolving. You should pay attention to the official documentation.

I/O documentation is mainly in: http://clojure.org/cheatsheet Io section.

Also: http://clojure.github.com/clojure/clojure.java.io-api.html

Also here can refer to: http://java.ociweb.com/mark/clojure/article.html#IO