13.htm

debian参考手册,pdf格式的版本。

               "  where:\n" \ 
               "    startUID is the starting userid to add, and\n" \
               "    file is an input file in form:\n" \
               "      first_name last_name password\n" \
             )
             exit
         }
     
         infile = ARGV[1]
         printf( "Starting UID: %s\n\n", startuid )
     }
     
     /^#/ { next }
     
     {
         ++record
         first = $1
         last = $2
         passwd = $3
         user= substr( tolower( first ), 1, 1 ) tolower( last )
         uid = startuid + record - 1
         gid = uid
         printf( "%s:%s:%d:%d:%s %s,,/home/%s:/bin/bash\n",  \
             user, passwd, uid, gid, first, last, user \
             )
     }
</PRE>
<P>Debian中有两个软件包提供了POSIX <CODE>awk</CODE>： 
<UL>
  <LI><CODE>mawk</CODE> 
  <UL>
    <LI>Priority: required 
    <LI>Installed-Size: 228 
    <LI>Smaller and much faster — good for default install 
    <LI>Compile-time limits exist 
    <UL>
      <LI>NF = 32767 
      <LI>sprintf buffer = 1020 </LI></UL></LI></UL>
  <LI><CODE>gawk</CODE> 
  <UL>
    <LI>Priority: optional 
    <LI>Installed-Size: 1708 
    <LI>Larger and featureful — many extensions implemented 
    <UL>
      <LI>System V Release 4 version of UNIX 
      <LI>Bell Labs awk 
      <LI>GNU-specific </LI></UL></LI></UL></LI></UL>
<HR>
<A name=s13.4></A>
<H2>13.4 Perl</H2>
<P>运行于类Unix系统上的<STRONG>解释器</STRONG>。 
<P>Perl参考资源： 
<UL>
  <LI><CODE>perl(1)</CODE> 
  <LI><EM>Programming Perl</EM>, 3rd edition (O'Reilly) </LI></UL>
<P>简短的程序样例（创建<CODE>newusers</CODE>命令输入）： <PRE>     #!/usr/bin/perl
     # (C) Osamu Aoki Sun Aug 26 16:53:55 UTC 2001 Public Domain
     $pid=1000;
     while (&lt;STDIN&gt;) {
             if (/^#/) { next;}
             chop;
             $pid++;
             ($n1, $n2, $n3) = split / /;
             print $n1,"_",$n2,":", $n3, ":",$pid,
                       ":",$pid,",,,/home/",$n1,"_",$n2,":/bin/bash\n"
     }
</PRE>
<P>安装Perl模块<VAR>module_name</VAR>： <PRE>     # perl -MCPAN -e 'install <VAR>module_name</VAR>'
</PRE>
<HR>
<A name=s13.5></A>
<H2>13.5 Python</H2>
<P>一个不错的面向对象的解释器。 
<P>Python参考资源： 
<UL>
  <LI><CODE>python(1)</CODE> 
  <LI><EM>Learning Python</EM> (O'Reilly). </LI></UL>
<P>简短的程序样例（创建<CODE>newusers</CODE>命令输入）： <PRE>     #! /usr/bin/env python
     import sys, string
     
     # (C) Osamu Aoki Sun Aug 26 16:53:55 UTC 2001 Public Domain
     # Ported from awk script by KMSelf Sat Aug 25 20:47:38 PDT 2001
     # This program is distributed WITHOUT ANY WARRANTY.
     
     def usages():
         print \
     "Usage:  ", sys.argv[0], " start_UID [filename]\n" \
     "\tstartUID is the starting userid to add.\n" \
     "\tfilename is input file name. If not specified, standard input.\n\n" \
     "Input file format:\n"\
     "\tfirst_name last_name password\n"
                     return 1
     
     def parsefile(startuid):
         #
         # main filtering
         #
         uid = startuid
         while 1:
             line = infile.readline()
             if not line:
                 break
             if line[0] == '#':
                 continue
             (first, last, passwd) = string.split(string.lower(line))
             # above crashes with wrong # of parameters :-)
             user = first[0] + last
             gid = uid
             lineout = "%s:%s:%d:%d:%s %s,,/home/%s:/bin/bash\n" %  \
                 (user, passwd, uid, gid, first, last, user)
             sys.stdout.write(lineout)
             +uid
     
     if __name__ == '__main__':
         if len(sys.argv) == 1:
             usages()
         else:
             uid = int(sys.argv[1])
             #print "# UID start from: %d\n" % uid
             if len(sys.argv) &gt; 1:
                 infilename   = string.join(sys.argv[2:])
                 infile = open(infilename, 'r')
                 #print "# Read file from: %s\n\n" % infilename
             else:
                 infile = sys.stdin
             parsefile(uid)
</PRE>
<HR>
<A name=s13.6></A>
<H2>13.6 Make</H2>
<P>Make参考资源： 
<UL>
  <LI><SAMP>info make</SAMP> 
  <LI><CODE>make(1)</CODE> 
  <LI><EM>Managing Projects with make</EM>, 2nd edition (O'Reilly) </LI></UL>
<P>简单自动变量： 
<P>语法规则： <PRE>     <VAR>target</VAR>: [ <VAR>prerequisites</VAR> ... ]
      [TAB]  <VAR>command1</VAR>
      [TAB]  -<VAR>command2</VAR> # ignore errors
      [TAB]  @<VAR>command3</VAR> # suppress echoing
</PRE>
<P>在此<SAMP>[TAB]</SAMP>代表一个TAB符。完成变量代换后shell将逐行进行解释。在行尾使用<SAMP>\</SAMP>可以续行。使用<SAMP>$$</SAMP>可将<SAMP>$</SAMP>加入到shell脚本的环境变量中。 

<P>适用于<VAR>target</VAR>和<VAR>prerequisites</VAR>的隐含的等价规则： <PRE>     %: %.c header.h
</PRE>
<P>or, <PRE>     %.o: %.c header.h
</PRE>
<P>在此，<VAR>target</VAR>包含了<SAMP>%</SAMP>字符（确切地说是其中之一），<SAMP>%</SAMP>可匹配实际的target文件名中任何非空子串。<VAR>prerequisites</VAR>同样也使用<SAMP>%</SAMP>来显示它们的名字是如何关联到实际的target文件名的。 

<P>用<STRONG>Suffix rules</STRONG>方法来定义<CODE>make</CODE>的隐含规则(implicit 
rules)已经<STRONG>过时</STRONG>。GNU 
<CODE>make</CODE>因为兼容性的考虑仍支持它，但只要有可能就应该使用与之等价的模版规则(pattern rules)： <PRE>     old suffix rule --&gt; new pattern rule
     .c:             --&gt; %  : %.c
     .c.o:           --&gt; %.o: %.c
</PRE>
<P>上述规则所使用的自动变量： <PRE>     foo.o: new1.c new2.c old1.c new3.c
     $@ == foo.o                         (target)
     $&lt; == new1.c                        (first one)
     $? == new1.c new2.c new3.c          (newer ones)
     $^ == new1.c new2.c old1.c new3.c   (all)
     $* == `%' matched stem in the target pattern.
</PRE>
<P>变量参考： <PRE>     foo1 := bar    # One-time expansion
     foo2  = bar    # Recursive expansion
     foo3 += bar    # Append
     SRCS := $(wildcard *.c)
     OBJS := $(foo:c=o)
     OBJS := $(foo:%.c=%.o) 
     OBJS := $(patsubst %.c,%.o,$(foo)) 
     DIRS  = $(dir directory/filename.ext) # Extracts "directory"
      $(notdir NAMES...), $(basename NAMES...), $(suffix NAMES...) ...
</PRE>
<P>执行<SAMP>make -p -f/dev/null</SAMP>可查看内部自动规则。 
<HR>
<A name=s13.7></A>
<H2>13.7 C</H2>
<P>准备工作： <PRE>     # apt-get install glibc-doc manpages-dev libc6-dev gcc
</PRE>
<P>C参考资源： 
<UL>
  <LI><SAMP>info libc</SAMP> (C library function reference) 
  <LI><CODE>gcc(1)</CODE> 
  <LI><CODE>each_C_library_function_name(3)</CODE> 
  <LI>Kernighan &amp; Ritchie, <EM>The C Programming Language</EM>, 2nd edition 
  (Prentice Hall). </LI></UL>
<HR>
<A name=s13.7.1></A>
<H3>13.7.1 简单C编程(<CODE>gcc</CODE>)</H3>
<P>一个简单的例子，将<CODE>example.c</CODE>和库函数<CODE>libm</CODE>编译成可执行文件<CODE>run_example</CODE>： 
A simple example to compile <CODE>example.c</CODE> with a library 
<CODE>libm</CODE> into an executable <CODE>run_example</CODE>: <PRE>     $ cat &gt; example.c &lt;&lt; EOF
     #include &lt;stdio.h&gt;
     #include &lt;math.h&gt;
     #include &lt;string.h&gt;
     
     int main(int argc, char **argv, char **envp){
             double x;
             char y[11];
             x=sqrt(argc+7.5);
             strncpy(y, argv[0], 10); /* prevent buffer overflow */
             y[10] = '\0'; /* fill to make sure string ends with '\0' */
             printf("%5i, %5.3f, %10s, %10s\n", argc, x, y, argv[1]);
             return 0;
     }
     EOF
     $ gcc -Wall -g -o run_example example.c -lm
     $ ./run_example
             1, 2.915, ./run_exam,     (null)
     $ ./run_example 1234567890qwerty
             2, 3.082, ./run_exam, 1234567890qwerty
</PRE>
<P>在此，sqrt()链接库函数<SAMP>lib<STRONG>m</STRONG></SAMP>需要<SAMP>-l<STRONG>m</STRONG></SAMP>选项。真正的库函数是位于<CODE>/lib</CODE>下的<CODE>libm.so.6</CODE>，它是<CODE>libm-2.1.3.so</CODE>的一个符号链接。 

<P>看看输出文本中最后的参数，尽管指定了<SAMP>%10s</SAMP>，它还是多于10个字符。 
<P>使用不带边界检查的指针内存操作函数如<CODE>sprintf</CODE>和<CODE>strcpy</CODE>会妨碍缓冲区溢出侦测，故使用<CODE>snprintf</CODE>和<CODE>strncpy</CODE>。 

<HR>
<A name=s13.7.2></A>
<H3>13.7.2 调试</H3>
<HR>
<A name=s13.7.2.1></A>
<H4>13.7.2.1 使用<CODE>gdb</CODE>进行调试</H4>
<P>准备工作： <PRE>     # apt-get install gdb
</PRE>
<P><CODE>gdb</CODE>参考资源： 
<UL>
  <LI><SAMP>info gdb</SAMP> (tutorial) 
  <LI><CODE>gdb(1)</CODE> 
  <LI><CODE><A 
  href="http://www.unknownroad.com/rtfm/gdbtut/gdbtoc.html">http://www.unknownroad.com/rtfm/gdbtut/gdbtoc.html</A></CODE> 
  </LI></UL>
<P>使用<SAMP>-g</SAMP>选项编译程序就可使用<CODE>gdb</CODE>进行调试。许多命令都可以缩写。Tab扩展功能和在shell中的一样。 
<PRE>     $ gdb program
     (gdb) b 1                # 在line 1设置断点
     (gdb) run <VAR>arg1 arg2 arg3</VAR> # 运行程序
     (gdb) next               # 下一行
     ...
     (gdb) step               # 前进一步
     ...
     (gdb) p parm             # 打印parm  
     ...
     (gdb) p parm=12          # 设置其值为12
</PRE>
<P>在Emacs环境下调试程序，参阅<A 
href="http://qref.sourceforge.net/Debian/reference/ch-edit.zh-cn.html#s-editkey">编辑器命令总汇（Emacs，Vim）, 
第 11.3.4 节</A>。 
<HR>
<A name=s-ss-ldd></A>
<H4>13.7.2.2 检查库函数关联关系</H4>
<P>使用<CODE>ldd</CODE>可查看程序与库函数的关联关系： <PRE>     $ ldd /bin/ls