304です。
以下が作成中のコードです。
void vis(char *name,FILE *fin)
{
FILE *fout;
int c, i;
char buf[BUFSIZ], *outfile="out_";

strcat(outfile,name);
printf("%s\n",outfile);

if((fout=fopen(outfile,"w"))==NULL){
printf("cannot open file!\n");
}

do{
for(i=0; (c=getc(fin)) != EOF ;){
if(!isprint(c)){
fprintf(fout,"\\X%X",c);
break;
}
buf[i++]=c;
if(i >= BUFSIZ)
break;
}
if(i >= MINLEN)
fprintf(fout,"%.*s\n",i, buf);
}while (c != EOF);

fclose(fout);
}