LINUX下编程入门.doc

Linux下编程入门by Luster一、介绍 使用了Linux一段时间后，很多朋友都希望能为这个开放辕马世界做自己的贡献，更多的参加到这个open source的社团里。面对无数的自由软件，对于一个稍微不太普通的用户来说去解开一个tar文件，然后修改makefile去编译辕马都是很常有的。我们不满足简单的编译和使用别人的程序，我们应该亲自参加到这个开发辕马的创作之中。对于一个初学者来说，面对五花八门的开发工具，如何选择呢？使用什么开发工具去开发Linux程序呢？我们这里做个简单的介绍。这里是你成为Linux hacker征途上的第一步。二、编程模式 让我们开始第一步。作为一个初学者应该首先使用什么样的编程风格或者说编程模式呢？有很多的选择，例如基于函数的、基于过程的开发，还有面向对象的开发等等。要成为一个好的programmer，对于初学者，最好使用某种语言对各种编程模式都尝试一遍。Comp.lang.functional讨论组里面的FAQ中定义了面向函数的语言，说“a style of programming that emphasizes the evaluation of expressions, rather than execution of commands. The expressions in these language are formed by using functions to combine basic values. A functional language is a language that supports and encourages programming in a functional style. 在Linux平台下面，比较常见的面向函数的开发语言有：ML、Haskell、Scheme等。面向过程的语言是一种把程序要完成的动作分割成一个一个“过程（procedures）”的语言。一个典型的面向过程的开发语言的组织结构，我们可以看看流程图，就可以感觉出来。最常见的面向过程的开发语言就是Pascal和C语言了。面向对象的开发语言的核心就是用对象来表征所要执行的主体。例如要开发一个高速公路的模拟系统，他首先定义一个交通工具的类，包括所有交通工具的公共属性；然后继承这个类，可以派生出汽车类、自行车类等等。Linux平台下最常见的面向对象的语言是C+、Java、Python、Smalltalk和Eiffel等。还有混合的语言，你可以用多种编程模式去写自己代码，例如PHP和Perl。如何选择？一般来说最好每种模式都有一个了解。最好这样开始你的编程旅程，首先给自己定一个小project。有了一个清晰的目标后，选择编程语言和编程模式就容易了。如果使用某种语言开发起来容易，那么你就先学习使用这种语言。例如，我开始想学习更多的关于数据库和web编程的时候，我决定建一个书籍数据库，包括我拥有的书的信息还有我要计划购买的书籍信息。经过我的查找比较，我认为我的想法可以用PHP和MySQL来实现更方便。然后我就学习了PHP和MySQL的一些知识，完成了这个小的系统。我个人的编程体会，我至少使用了4种语言，包括：C、PHP、SQL和Perl。C语言是最灵活和方便的开发语言，在Linux下使用最多的开发语言就是它了。一旦学会了C语言，我们就可以非常容易的学习和使用其他的语言了。所以我建议你学习C语言编程。C语言是一种高级语言，它编写内核级的代码和驱动程序都非常方便。Linux下面有很多开发C语言的函数库和开发工具，我们都可以方便的使用它们，这也是使用C语言开发代码的好处。PHP是Hyper-text Processor的缩写，是一种解释执行的语言，一般来说运行在web服务器端。如果你会C语言，那么最多花一天的时间就可以学会PHP。PHP给你在web编程方面很大的方便。SQL是Standard Query Language的缩写，就是标准的访问数据的查询语言。很多PHP程序中都包含了使用SQL语言去访问数据库的代码。SQL基本上使用有点类似英文的语法，所以学起来非常容易。如果你学习PHP和C，那么SQL可以简单的顺便学习。Perl是一种使用比较广的教本语言。很多语法来自C和UNIX的SHELL工具。Perl拥有很多的可以添加的模块，在CPAN计划中。使用这些模块，开发程序编得非常容易了。 下面是一个perl程序例子：#!/usr/bin/perl # NMSU Job grabber # Matt Michie ()#-#Copyright (c) 2000, Matt Michie () (All rights reserved.)#Redistribution and use in source and binary forms, with or without #modification, are permitted provided that the following conditions are met:#Redistributions of source code must retain the above copyright notice, #this list of conditions and the following disclaimer.#Redistributions in binary form must reproduce the above copyright notice,#this list of conditions and the following disclaimer in the documentation#and/or other materials provided with the distribution.#The names of this programs contributors may not be used to endorse or #promote products derived from this software without specific prior #written permission. #THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS#AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT #LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR #A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR #CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, #EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, #PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; #OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,#WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR #OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF #ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #-#Instructions for use:#You must have LWP installed to fetch the jobs. If you wish to use the#e-mail notification you also must have sendmail installed.#The script has the following command line flags:#-v : Print the version#-t : Max threshold to include the salary in statistics calculations#-b (number) : Boundary of salary after which program will shoot off an # e-mail#-m (email address) : Tell the program to notify you with email. The arguement# is a valid e-mail address. #-q : Quiet mode, dont print statistics, automatically used in email mode.#Example use:#fetch.pl -b 7.50 -m #This tells the program to fetch the jobs list and only send e-mail #notification if there are any jobs with higher pay than $7.50.#-use LWP:Simple;use Getopt:Std;$version = Job Grabber 0.01;getopts(vqt:m:b:) | die Check your command line args! ;if ($opt_t != 0) $max = $opt_t;else $max = 20; # Max threshold to include salary in count$min = 0; # Min threshold to include salary in count$highest = 0; # Highest salary$total = 0; # Total jobs counted$count = 0; # Total jobs which fall inside min/max thresholds$oncampus = /pment/oncampu.htm;#$offcampus = /pment/offcampu.htm;$URL = $oncampus;if ($opt_v) print $version ; exit(0);if ($opt_m & !$opt_q) $opt_q = true;&fetch_page;&stats;if ($opt_m & ($highest $opt_b) &email;elsif (!$opt_b & $opt_m) $opt_q = 1;sub fetch_page unless (defined ($page = get($URL) die There was an error getting URL: $URL ; page = split(/ /, $page); foreach $line (page) $line = s/*/g; # strip HTML codesif (!$opt_q & $line = /On campus job postings as of:/) print $line ;elsif ($line = /SALARY:/) push pay, (split (/:/, $line)1; sub stats foreach $elm (pay) $total+;next if ($elm = $max); if ($elm $highest) $highest = $elm;$count+; $accum += $elm; if ($count = 0) die Eiiiiiiiiiieeeeeeeeeeeeeeeeeeee divide by zero :( ; else $avg = $accum / $count; if (!$opt_q) print Total jobs listed: $total ;print Number of jobs counted for pay: $count ;print Highest hourly pay: $highest ;printf Average hourly pay: $%.2f , $avg; sub email open(SENDMAIL, |/usr/lib/sendmail -oi -t -odq)or die Cant fork for sendmail: $! ;print SENDMAIL EOF;From: Job Grabber To: $opt_m Subject: JobbyTotal jobs listed: $totalNumber of jobs counted for pay: $countHighest hourly pay: $highest Average hourly pay: $avg EOF close(SENDMAIL) or warn sendmail didnt close nicely;从上面的代码中你可以看到，大部分的代码都是“过程”，使用与C类似的