C小程序 - 模拟more

978阅读　0评论2012-10-26　niannian
分类：C/C++

摘自《linux-unix编程实践》

  1. #include    <stdio.h>
  2. #include    <signal.h>
  3. #include    <termios.h>

  5. #define    LINELEN    512
  6. #define    oops(s) { perror(s); exit(1); }

  8. void do_more(FILE *);
  9. int see_more(FILE *);

  11. int main(int ac,char *av[])
  12. {
  13.     FILE    *fp;
  14.     int    rv = 0;

  16.     settings(0);
  17.     if ( ac == 1 )
  18.         do_more(stdin);
  19.     else
  20.         while ( --ac )
  21.             if ( (fp=fopen(*++av,"r")) != NULL ) {
  22.                 do_more(fp) ;
  23.                 fclose(fp);
  24.             }
  25.             else {
  26.                 perror(*av);
  27.                 rv = 1;
  28.                 break;
  29.             }
  30.     settings(1);
  31.     return rv;
  32. }

  34. /*
  35.  * * called for SIGINT and SIGQUIT
  36.  * * - Just reset terminal and get out
  37.  * */
  38. void handler(int s)
  39. {
  40.     settings(1);
  41.     exit(0);
  42. }

  44. /*
  45.  * * program settings are turned on and off here
  46.  * */
  47. settings(int how)
  48. {
  49.     void handler(int);
  50.     int    rv;

  52.     static struct termios    term_orig;

  54.     /* read settings */
  55.     if ( how == 0 )
  56.     {
  57.         struct termios        term_new;

  59.         rv = tcgetattr(0, &term_orig);    /* get settings */
  60.         if ( rv == -1 )
  61.             oops("getting settings");
  62.         term_new = term_orig;
  63.         term_new.c_lflag &= ~ICANON;    /* noncanonical    */
  64.         term_new.c_lflag &= ~ECHO;    /* no echo     */
  65.         term_new.c_cc[VMIN] = 1;    /* chr-by-chr    */

  67.         rv = tcsetattr(0, TCSANOW, &term_new);
  68.         if ( rv == -1 )
  69.             oops("changing settings");

  71.         signal(SIGINT,handler);
  72.         signal(SIGQUIT,handler);
  73.     }
  74.     else
  75.     {
  76.         tcsetattr(0, TCSANOW, &term_orig);
  77.     }
  78. }

  80. void do_more( FILE *fp )
  81. /*
  82.  * * read PAGELEN lines, then call see_more() for further instructions
  83.  * */
  84. {
  85.     char    line[LINELEN];
  86.     FILE    *fp_tty;
  87.     int    num_of_lines = 0;
  88.     int    see_more(FILE *), reply;
  89.     int    pagelen = screen_rows(1);

  91.     fp_tty = fopen( "/dev/tty", "r" );     /* NEW: cmd stream */
  92.     if ( fp_tty == NULL )             /* if open fails */
  93.         exit(1); /* no use in running */

  95.     while ( fgets( line, LINELEN, fp ) ){        /* more input    */
  96.         if ( num_of_lines == pagelen ) {    /* full screen?    */
  97.             reply = see_more(fp_tty); /* NEW: pass FILE * */
  98.             if ( reply == 0 )        /* n: done */
  99.                 break;
  100.             if ( reply == -1 )
  101.                 num_of_lines = 0;
  102.             else
  103.                 num_of_lines -= reply;    /* reset count    */
  104.         }
  105.         if ( fputs( line, stdout ) == EOF )    /* show line    */
  106.             exit(1);            /* or die    */
  107.         num_of_lines++;                /* count it    */
  108.     }
  109. }

  111. int see_more(FILE *cmd)                 /* NEW: accepts arg */
  112. /*
  113.  * *    print message, wait for response, return # of lines to advance
  114.  * *    q means no, space means yes, CR means one line
  115.  * *    Returns -1 for spacebar (ie. full screen)
  116.  * */
  117. {
  118.     int    c;

  120.     printf("\033[7m more? \033[m");        /* reverse on a vt100    */
  121.     while( (c=getc(cmd)) != EOF )        /* NEW: reads from tty */
  122.     {
  123.         printf("\r \r");        /* erase message    */
  124.         if ( c == 'q' )            /* q -> N        */
  125.             return 0;
  126.         if ( c == ' ' )            /* ' ' => next page    */
  127.             return -1;        /* -1 means full page    */
  128.         if ( c == '\n' )        /* Enter key => 1 line    */
  129.             return 1;        
  130.         printf("\033[7m more? \033[m");    /* put it back        */
  131.     }
  132.     return 0;
  133. }

  135. #include <sys/ioctl.h>

  137. /*
  138.  * * returns the number of rows associated with fd
  139.  * * or 24 if that number cannot be determined
  140.  * */
  141. int
  142. screen_rows(fd)
  143. {
  144.     struct winsize wbuf;

  146.     if ( ioctl(fd, TIOCGWINSZ, &wbuf) != -1 )
  147.         return wbuf.ws_row;
  148.     return 24;
  149. }

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