unix下more命令的简单实现：

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

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

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

int do_more(FILE * fp)
{
	char buffer[LINELEN];
	int number_of_lines = 0;
	int reply;
	FILE * ftty;
	ftty = fopen("/dev/tty","r");
	if(ftty == NULL)
		exit(1);
	while(fgets(buffer,LINELEN,fp))
	{
		if(number_of_lines == PAGELEN)
		{
			fputs(buffer,stdout);
			reply = see_more(ftty);
			if(reply == 0)
				break;
			if(reply == 1)
				number_of_lines = 0;
			//if(reply == 2)
			//	number_of_lines--;
		}
		else
		{
			number_of_lines++;
			fputs(buffer,stdout);
		}
	}
}

int see_more(FILE * fp)
{
	char c;
	printf("enter your command(q space or enter):");
	while((c = getc(stdin)) != EOF)
	{
	if(c == 'q')//按q退出
		return 0;
	if(c == ' ')
		return 1;//按空格显示下一页
	if(c == 'n')
		return 2;//按n显示下一行
	}
	return 3;
}

自己动手写shell命令之more