UNIX/LINUX编程实战教程——读书笔记一

UNIX/LINUX编程实战教程读书笔记 ，开篇以more指令来进入：

more可以分页显示文件的内容，大部分的Unix系统都有文本文件“ /etc/termcap”，我使用的CentOS上也有，它经常被文本编辑器和游戏程序用到，那么用“ cat /etc/termcap”来查看的时候，通常一页是显示不完，太长了，这样more的价值出来了，使用“more ****”或者“cat **** | more”。

SO，它会显示文件第一屏的内容，在屏幕的底部，more用反白字体显示文件的百分比，这时如果按空格键，文件的下一屏内容会显示出来，如果按回车键，显示的则是下一行，如果输入“q”，结束显示，如果输入“h”，显示出来的是more的联机帮助。

本书在后面用它提及的方法来展示了自己编写more功能的代码，下面会把它贴上来 ，有个地方不会一样，就是觉得17面的程序中，因为它全局已经声明了一下“int see_more（）；”，我就在do_more（）函数里把“int see_more（）”给注释了。还是要多看看代码：

/*more01.c -- version 0.1 of more *read and print 24 lines then pause for a few special commands */ #include <stdio.h> #include <stdlib.h> #define PAGELEN 24 #define LINELEN 512 void do_more(FILE *); int see_more(); int main(int ac, char *av[]) { FILE *fp; if(ac == 1) do_more(stdin); else while(--ac) { if((fp=fopen(* ++av,"r"))!= NULL) { do_more(fp); fclose(fp); } else exit(1); } return 0; } /* *read PAGELEN lines, then call see_more() for further instructions */ void do_more(FILE *fp) { char line[LINELEN]; int num_of_lines = 0; // int see_more(), reply; int reply; while(fgets(line,LINELEN,fp)) { if(num_of_lines == PAGELEN) { reply = see_more(); if(reply == 0) break; num_of_lines -= reply; } if(fputs(line,stdout) == EOF) exit(1); num_of_lines++; } } /* *print message, wait for reponse, return # of lines to advance *q means no, space means yes, CR means one line */ int see_more() { int c; printf("\033[7m more?\033]"); while((c=getchar())!= EOF) { if(c == 'q') return 0; if(c == ' ') return PAGELEN; if(c == '\n') return 1; } return 0; }
下面一个是在以上面为基础而更完善的一点功能的程序：

/*more02.c -- version 0.2 of more *read and print 24 lines then pause for a few special commands *feature of version of 0.2: reads from /dev/tty for commands */ #include <stdio.h> #include <stdlib.h> #define PAGELEN 24 #define LINELEN 512 void do_more(FILE *); int see_more(FILE *); //it is different from more01.c, //"Note" stands for this difference. int main(int ac, char *av[]) { FILE *fp; if(ac == 1) do_more(stdin); else while(--ac) { if((fp=fopen(* ++av,"r"))!= NULL) { do_more(fp); fclose(fp); } else exit(1); } return 0; } /* *read PAGELEN lines, then call see_more() for further instructions */ void do_more(FILE *fp) { char line[LINELEN]; int num_of_lines = 0; // int see_more(), reply; int reply; FILE *fp_tty; //Note fp_tty = fopen("/dev/tty","r"); //Note if(fp_tty == NULL) //Note exit(1); //Note while(fgets(line,LINELEN,fp)) { if(num_of_lines == PAGELEN) { reply = see_more(fp_tty); //Note if(reply == 0) break; num_of_lines -= reply; } if(fputs(line,stdout) == EOF) exit(1); num_of_lines++; } } /* *print message, wait for reponse, return # of lines to advance *q means no, space means yes, CR means one line */ int see_more(FILE *cmd) //Note { int c; printf("\033[7m more? \033[m"); while((c=getc(cmd))!= EOF) //Note { if(c == 'q') return 0; if(c == ' ') return PAGELEN; if(c == '\n') return 1; } return 0; }
本书后面还留了点问题，可以更加完善后就和系统的more指令完成的功能一样了。后面会通过学习来解决它的。先到这样。