fscanf和fprintf
fscanf的字符串是在键盘的缓冲区，fprintf是在显示器的缓冲区。
1.函数原型：
- int fprintf(FILE *fp， const char *format[,argument, ...])
- int fscantf(FILE *fp， const char *format[,address, ...])
2.功能：按格式对问件进行I/O操作
3.返回值：
- 成功，返回I/O的个数，出错或文件尾，返回EOF。
- fprintf()返回值就是写入成功的字符的个数。
- fscanf()返回值是扫描到几个数据，这个字符串不管有多长，要扫描的每一种类型算一个数据，%s算一个，%d算一个。详见eg3.
4.例子：
fprintf(fp, "%d, %6.2f, i,t"); //将i和t按%d,%6.2f格式输出到fp文件
fscanf(fp, "%d,%f", &i,&t)/ //若文件中有3，4.5，则将3送入i，4.5送入t。
eg1:
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include <stdlib.h> void main1()
{
//printf("hello");
//fprintf(stdout, "hello");//printf只是fprintf特例
char str[] = { };
//scanf("%s", str);
fscanf(stdin, "a=%s", str);//从字符串中取出，键盘缓冲区,输入时，要输入“a=abc”,下面才会打印。
fprintf(stdout, "%s", str);//int string映射到一个字符串 显示器缓冲区 getchar();
getchar(); }
//1 [email protected] xijaxi16ytja6t7ibcrj
void main2()
{ char str[] = { };
{
int i = ;
char email[] = "[email protected]";
char password[] = "xijaxi16ytja6t7ibcrj"; sprintf(str, "%d %s %s", i, email, password);
fprintf(stdout, "\n%s", str);
}
{
int j;
char emailx[] = { };
char passmd5[] = { };
sscanf(str, "%d%s%s", &j, emailx, passmd5);
fprintf(stdout, "\nj=%d eamilx=%s passmd5=%s ", j, emailx, passmd5); } system("pause");
}
eg2:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h> typedef struct info7k7k
{
char user[];
char password[]; }INOF,* PINOF; void main2x()
{
FILE *pfr = fopen("Z:\\I\\尹成清华终极版C语言视频源码文档20150131\\大数据相关数据\\7k7k2000万_2047\\2000-1\\7k7kOK.txt", "r");
FILE *pfw = fopen("Z:\\I\\尹成清华终极版C语言视频源码文档20150131\\大数据相关数据\\7k7k2000万_2047\\2000-1\\7k7kOKwithid.txt", "w");
int i = ;
while (!feof(pfr))
{
i++;
INOF info1;
fscanf(pfr, "%s%s", info1.user, info1.password);//提取
fprintf(pfw, "%d %s %s\n", i, info1.user, info1.password);//组合
}
fclose(pfr);
fclose(pfw);
system("pause");
} void main3x()
{
//int num = fprintf(stdout, "helloword%s","1234");
//printf("\n%d", num);//fprintf返回值就是写入成功字符的个数
FILE *pf = fopen("C:\\x.txt", "r");
int num = fprintf(pf, "helloword%s", "");//写入失败返回-1
printf("\n%d", num);
system("pause");
}
void main()
{
//char str[128] = { 0 };
//int numa;
//int numb;
//int num = fscanf(stdin, "%s%d%d",str,&numa,&numb);
////返回值是扫描到几个数据,失败返回-1
//printf("\n%d", num);
FILE *pf = fopen("C:\\x.txt", "w");
char str[] = { };
int numa;
int numb;
int num = fscanf(pf, "%s%d%d",str,&numa,&numb);
printf("\n%d", num); system("pause"); }
eg3:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h> typedef struct info
{
char user[];
char password[]; }INOF,* PINOF; void main2x()
{
FILE *pfr = fopen("Z:\\I\\尹成清华终极版C语言视频源码文档20150131\\大数据相关数据\\7k7k2000万_2047\\2000-1\\7k7kOK.txt", "r");
FILE *pfw = fopen("Z:\\I\\尹成清华终极版C语言视频源码文档20150131\\大数据相关数据\\7k7k2000万_2047\\2000-1\\7k7kOKwithid.txt", "w");
int i = ;
while (!feof(pfr))
{
i++;
INOF info1;
fscanf(pfr, "%s%s", info1.user, info1.password);//提取
fprintf(pfw, "%d %s %s\n", i, info1.user, info1.password);//组合
}
fclose(pfr);
fclose(pfw);
system("pause");
} void main3x()
{
//int num = fprintf(stdout, "helloword%s","1234");
//printf("\n%d", num);//fprintf返回值就是写入成功字符的个数
FILE *pf = fopen("C:\\x.txt", "r");
int num = fprintf(pf, "helloword%s", "");//写入失败返回-1
printf("\n%d", num);
system("pause");
}
void main()
{
//char str[128] = { 0 };
//int numa;
//int numb;
//int num = fscanf(stdin, "%s%d%d",str,&numa,&numb);
////返回值是扫描到几个数据,失败返回-1
//printf("\n%d", num);
FILE *pf = fopen("C:\\x.txt", "w");
char str[] = { };
int numa;
int numb;
int num = fscanf(pf, "%s%d%d",str,&numa,&numb);
printf("\n%d", num); system("pause"); }