#include <stdio.h>
#include <stdlib.h>
#include<ctype.h>

#define iskanji(c)\
(0x81 <= (c & 0xff)&&(c & 0xff) <= 0x9f || 0xe0 <= (c & 0xff) && (c & 0xff) <= 0xfc)

main(int ac, char *av)
{
FILE *fp;
++av;
if(av==0){
exit(1);
}

fp=fopen(av,"r");
char c;
while((c=fgetc(fp))!=EOF){
if(iskanji(c)){
fputc(c,stdout);
fputc(fgetc(fp),stdout);
}
else
{
fputc(c,stdout);
}

}
}
segmentation faultになったよ　なぜ