/*
编写一段程序,将一个字符, 零个或多个文件名作为命令行参数.
如果字符后没有参数跟随,程序读取标准输入文件.
否则,程序依次打开每个文件,然后报告每个文件中该字符的出现次数.
文件名和字符本身也与计数值一起报告.
程序中包括错误检查,以确定参数数目是否正确和是否能打开文件.
如果不能打开文件,程序要报告这一情况然后继续处理下一文件. 
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define SIZE 40

void input(char *, char **);
void savename(int, char **, char *);
void search(char, FILE *, char *);

int main(int argc, char **argv)
{
	char file[SIZE];
	
	switch(argc){
	case 1:exit(1);
	case 2:input(file, argv);break;
	default:savename(argc, argv, file);break;
	}
	
	puts("Done.");
	return 0;
}

void input(char *file, char **argv)
{
	FILE *fp;
	printf("Enter file name (newline to quit): ");
	while(scanf("%s", file) && file[0] != '\n')
	{
		if((fp = fopen(file, "r")) == NULL)
		{
			fprintf(stderr, "Can't open file %s.\n", file);
			printf("Enter file name (newline to quit): ");
			continue;
		}
		search(*argv[1], fp, file);
		fclose(fp);
		printf("Next file name (newline to quit): ");
	}
}

void savename(int n, char **source, char *file)
{
	int i = 2;
	FILE * fp;
	
	while(i < n)
	{
		file = source[i++];
		if((fp = fopen(file, "r")) == NULL)
		{
			fprintf(stderr, "Can't open file %s.\n", file);
			continue;
		}
		search(*source[1], fp, file);
		fclose(fp);
	}
}

void search(char ch, FILE * fp, char *file)
{
	char s;
	unsigned int count = 0;
	
	while((s = fgetc(fp)) != EOF)
	{
		if(s == ch)
			count++;
	}
	fprintf(stdout, "file: %s. %c sum = %u\n", file, ch, count);
}