happy_1[1]% cat kadai11-1.c
#include <stdio.h>

main()
{
    char s[10000];
    char fin[100];
    char fout[100];
    int n;
    int i;
    int a;
    FILE *in,*out;
  
    printf("Input file name: ");	/* ファイル名の入力 */
    scanf("%s",fin);
    printf("Output file name: ");
    scanf("%s",fout);

    if ((in=fopen(fin,"r"))==NULL) {	/* ファイルオープン */
	    exit(1);
    }
    if ((out=fopen(fout,"w"))==NULL) {
	    exit(1);
    }

    fgets(s,10000,in);	/* 入力 */

    n=0;
    i=0;
    a=0;

    while( s[i] != 0 ){
        if((s[i]>='a' && s[i]<='z') || (s[i]>='A' && s[i]<='Z')){
             if( a == 0 ){
                  n = n + 1;
             }
                  a = 1;
             }else{
                  a = 0;
        }
        i = i + 1;
    }


    fprintf(out,"String= %s \n", s );	/* 出力 */
    fprintf(out,"Word count=%d\n", n ); 

    fclose(in);	/* クローズ */
    fclose(out);
}

happy_1[2]% gcc -o kadai11-1 kadai11-1.c
happy_1[3]% cat test.txt
If you have any questions, raise your hands.
happy_1[4]% kadai11-1
Input file name: test.txt
Output file name: result.txt
happy_1[5]% cat result.txt
String= If you have any questions, raise your hands.
 
Word count=8