BLP.3th.editon--Learning Processing

ch03:Working with Files
    3.4 low-level file access
       The system calls most frequently used are the "write", "read", "open".(also, there are some others to be used, but used less.) Unfortunately, the system calls are less efficent than the library function calls, because Linux should switch from running U program code to excute its own kernel cod and back again.
    3.5 the standard I/O library
       Including the fopen, fwrite, fread, fclose, and so on.


与文件有关的几个库函数：
    1.fopen(),fread(),fwrite(),fclose(),fflush()  //针对文件流
    2.fgetc(),fputc(),fgets()  //针对文件流
    3.putchar(),getchar()      //只针对标准I/O
    ** 没有fputs()

ch04  The Linux Environment
    4.1 program arguments
       这一节主要介绍了有关程序命令行参数的处理，主要涉及两个函数：getopt(),getopt_long()。GUN的getopt()函数与标准C的getopt()函数略有区别，GNU在得到参数后，会先扫描，将所有选项和选项的关联值分别各自归到一起，即选项组成一个字符（串）数组，选项的关联项也形成一个字符（串）数组。在各自归类成组后，再分别处理。
    4.2 environment viarables