Linux中more命令的实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define PAGELEN 24
#define LINELEN 512

void do_more(FILE *);
int see_more(FILE *);

int main(int argc, char *argv[])
{
    FILE *fp;
    if (argc == 1)
        do_more(stdin);
    else
    {   
        while (--argc)
        {   
            if ((fp = fopen(*++argv, "r")) != NULL)
            {   
                do_more(fp);
                fclose(fp);
            }   
            else
                exit(1);
        }   
    }   
    return 0;
}

void do_more(FILE *fp)
{
    char line[LINELEN];
    int num_of_lines = 0;
    int reply;
    FILE *fp_tty;
    fp_tty = fopen("/dev/tty", "r");
    if(fp_tty == NULL)
        exit(1);
    while (fgets(line, LINELEN, fp))
    {
        if (num_of_lines == PAGELEN)
        {
            reply = see_more(fp_tty);
            if(reply == 0)
                break;
            num_of_lines -= reply;
        }
        if (fputs(line, stdout) == EOF)
            exit(1);
        num_of_lines++;
    }
}

int see_more(FILE *cmd)
{
    int c;
    printf("\033[7m more? \033[m");
    while ((c = getc(cmd)) != EOF)
    {
        if (c == 'q')
            return 0;
        if (c == ' ')
            return PAGELEN;
        if (c == '\n')
            return 1;
    }
    return 0;
}

还有许多缺陷