C言語基礎11

                     ，      
int *values[3];

               

           ，             ，      
int (*p_values)[3];
               
       ，              

FILE                 

fopen          ，       NULL，    FILE        。
        
                ，    
'r' :          ，        
'w' :          ，             
          ，         
'a' :          ，             
             

       '+'  ，     。                。

       'b'  ，     。                    。

fclose          ，     FILE       

fputc               ，       EOF。
fgetc                  ，       EOF。

fread fwrite                     

rewind                   

fseek                   ，       
SEEK_SET  : 0          
SEEK_CUR  : 1              
SEEK_END  : 2          

ftell                          

fgets            。
fputs              。

fprintf                 
fscanf                   

atoi              
atof               
sprintf                    
sscanf                        



/*
	      
*/
#include <stdio.h>
int main(int argc, char *argv[]) {
    int values[] = {6, 3, 7}, loop = 0;
	 int *p_value = NULL;
	 int *p_values[3] = {values, values + 1, values + 2};
    /*p_value = p_values[0];
	 p_values[0] = p_values[1];
	 p_values[1] = p_value;*/
	 p_value = p_values[1];
    p_values[1] = p_values[2];
	 p_values[2] = p_value;

	 p_value = p_values[0];
    p_values[0] = p_values[1];
	 p_values[1] = p_value;
	 for (loop = 0; loop <= 2; loop++) {
        printf("%d ", *p_values[loop]);
	 }
	 printf("
");
    return 0;
}


/*
	       
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int compare(const void* p_value, const void* p_value1) {
    const char** p_str = (const char**)p_value;
	 const char** p_str1 = (const char**)p_value1;
	 return strcmp(*p_str, *p_str1);
}
int main() {
    char *str[] = {"China", "France", "England", "Russia", "America"};
    int loop = 0;
    qsort(str, 5, sizeof(char*), compare);
	 for (loop = 0; loop <= 4; loop++) {
        printf("%s
", str[loop]);
	 }
    return 0;
}



/*
	      
*/
#include <stdio.h>
int main() {
    int values[2][3] = {0};
	 //int **pp_values = values;
	 int (*p_values)[3] = values;
	 /*printf("%p
", pp_values[0]);
	 printf("%d
", pp_values[0][0]);*/
	 printf("%d
", values[0][0]);
	 printf("%d
", p_values[0][0]);
	 values[1][1] = 3;
	 printf("%d
", p_values[1][1]);
	 printf("%p, %p
", p_values, p_values + 1);
    printf("%p, %p
", values, values + 1);
    return 0;
}


/*
	    
*/
#include <stdio.h>
int main() {
    FILE *p_file = fopen("a.txt", "w");
	 if (p_file) {
        //      
        fclose(p_file);
		  p_file = NULL;
	 }
    return 0;
}



/*
	    
*/
#include <stdio.h>
int main() {
    FILE *p_file = fopen("a.txt", "w");
	 if (p_file) {
        //      
        char str[] = "Hello China!";
		  int pos = 0;
		  while (str[pos] != 0) {
            if (EOF == fputc(str[pos], p_file)) {
                break;
				}
				pos++;
		  }
        fclose(p_file);
		  p_file = NULL;
	 }
    return 0;
}



/*
	    
*/
#include <stdio.h>
int main() {
    FILE *p_file = fopen("a.txt", "r");
	 if (p_file) {
        //      
              char ch = 0;
	      while (EOF != (ch = fgetc(p_file))) {
                   printf("%c", ch);
	      }
	       printf("
");
               fclose(p_file);
	       p_file = NULL;
	 }
    return 0;
}

/*
	    
*/
#include <stdio.h>
int main() {
    FILE *p_file = fopen("a.txt", "r");
	 if (p_file) {
        //      
        char buf[20];
		int size = 0;
        while (EOF != (buf[size] = fgetc(p_file))) {
            size++;
		}
        fclose(p_file);
		p_file = NULL;
		p_file = fopen("a.txt", "w");
		if (p_file) {
            size--;
			while (size >= 0) {
                if (EOF == fputc(buf[size], p_file)) {
                    break;
				}
				size--;
			}
			fputc('
', p_file);
			fclose(p_file);
			p_file = NULL;
		}
	}
    return 0;
}

/*
	    
*/
#include <stdio.h>
int main() {
    int values[] = {1, 2, 3};
    FILE *p_file = fopen("a.bin", "wb");
	 if (p_file) {
        //      
        int size = fwrite(values, sizeof(int), 3, p_file);
		  printf("   %d   
", size);
        fclose(p_file);
		  p_file = NULL;
	 }
    return 0;
}


/*
	    
*/
#include <stdio.h>
int main() {
    int values[3] = {0}, loop = 0;
    FILE *p_file = fopen("a.bin", "rb");
	 if (p_file) {
        //      
        int size = fread(values, sizeof(int), 3, p_file);
		  printf("   %d   
", size);
		  for (loop = 0; loop <= 2; loop++) {
            printf("%d ", values[loop]);
		  }
		  printf("
");
        fclose(p_file);
		  p_file = NULL;
	 }
    return 0;
}


/*
	    
*/
#include <stdio.h>
int main() {
    FILE *p_file = fopen("a.txt", "r");
	 if (p_file) {
        //      
        char ch = 0;
		  fseek(p_file, 3, SEEK_SET);
		  ch = fgetc(p_file);
		  printf("%c ", ch);
		  //rewind(p_file);
		  fseek(p_file, 3, SEEK_CUR);
		  ch = fgetc(p_file);
		  printf("%c ", ch);
		  //rewind(p_file);
		  fseek(p_file, -2, SEEK_END);
		  ch = fgetc(p_file);
		  printf("%c ", ch);
		  printf("
");
        fclose(p_file);
		  p_file = NULL;
	 }
    return 0;
}


/*
	        
*/
#include <stdio.h>
#include <stdarg.h>
int max (int cnt, ...) {
    int ret = 0, loop = 0;
	 va_list v;
	 va_start(v, cnt);
	 for (loop = 0; loop < cnt; loop++) {
        int value = va_arg(v, int);
		  if (value > ret) {
            ret = value;
		  }
	 }
	 va_end(v);
	 return ret;
}
int main() {
    printf("     %d
", max(3, 6, 32, 17));
	 printf("     %d
", max(4, 2, 9, 7, 3));
    return 0;
}




static void trace(const char *format, ...){
	FILE *fp = NULL;
	va_list args;

	fp = fopen("/var/tmp/whj.txt", "a+");
	if (fp){
		va_start(args, format);
		vfprintf(fp, format, args);
		fflush(fp);
		va_end(args);
		fclose(fp);
	}
}


*/
#include <stdio.h>
#include <stdlib.h>
int main() {
    char str[20] = {0};
    int value = atoi("328");
	 double d = atof("4.78");
	 printf("value %d
", value);
	 printf("d %lg
", d);
	 printf("%d %lg
", value, d);
	 sprintf(str, "%d %lg
", value, d);
	 printf("%s", str);
	 value = 0;
	 d = 0.0;
	 sscanf(str, "%d %lg", &value, &d);
	 printf("value %d,d %lg
", value, d);
    return 0;
}