#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdbool.h>
bool isA2z(char c)
{
	bool bl = true;
	if(!((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '-'))
	{
		bl = false;
	}
	return bl;
}
bool isword(char s[])
{
	bool bl = true;
	int i = 0;
	for(i = 0; i < strlen(s); i++)
	{
		if(!isA2z(s[i]))
		{
			return false;
		}
	}
	return bl;
}
bool format(char s[20])
{
	bool bl = true;
	int i = 0;
	int j = 0;
	char s_temp[20];
	s_temp[0] = 127;
	for(i = 0; i < strlen(s); i++)
	{
		if(isA2z(s[i]))
		{
			s_temp[j] = s[i];
			j++;
		}
	}
	if(s_temp[0] == 127)
	{
		return false;
	}
	s_temp[j] = '\0';
	j = 0;
	for(i = 0; i < strlen(s_temp); i++)
	{
		s[i] = s_temp[i];
		j++;
	}
	s[j] = '\0';
	return bl;
}
int main(void)
{
	int k = 1;
	printf("————————欢迎使用文本统计程序————————\n");
	while (k)
	{
		FILE *fp;
		FILE *fp_sort;
		char word[20];
		char filename[20];
		int sort[27];
		sort[26] = 0;
		printf("请输入要统计的文件的文件名:\n");
		scanf("%s", &filename); 
		int i = 0;
		char filename_sort[20] = "a.txt";
		printf("统计结果如下：\n");
		for(i = 0; i < 26; i++)
		{
			sort[i] = 0;
			filename_sort[0] = 'a' + i;
			if((fp_sort = fopen(filename_sort, "w")) == NULL)
			{
				printf("Child file open error!\n");
				exit(0);
			}
			if((fp = fopen(filename, "r")) == NULL)
			{
				printf("File open error!\n");
				exit(0);
			}
			while (!feof(fp))
			{
				fscanf(fp, "%s", &word);
				if(format(word))
				{
					if(word[0] == 'a' + i || word[0] == 'A' + i)
					{
						fputs(word, fp_sort);
						fputs(" ", fp_sort);
						sort[i]++;
						sort[26]++;
					}
				}
			}
			fclose(fp_sort);
			fclose(fp);
			printf("以字母%c开头的单词共有%d个\n", 'a' + i, sort[i]);
		}
		printf("本文单词总数为%d个\n", sort[26]);
		printf("输入数字0退出，输入其他数字继续统计下一篇\n");
		scanf("%d", &k);
	}
	return 0;
}

这个是在linux下运行的版本