fscanf函数用法及注意事项

/*FSCANF.C:This program writes formatted data to afile.It then uses fscanf to read the various databackfromthefile.*/

#include <stdio.h>

FILE *stream;

int main(void)

{

long l;

float fp;

char s[81];

char c;

stream=fopen("fscanf.out","w+");

if(stream==NULL)

printf("The file fscanf.out was not opened\n");

else

{

fprintf(stream,"%s%ld%f%c","a-string",

65000,3.14159,‘x‘);

/*Set pointer to beginning of file:*/

fseek(stream,0L,SEEK_SET);

/*Readdatabackfromfile:*/

fscanf(stream,"%s",s);

fscanf(stream,"%ld",&l);

fscanf(stream,"%f",&fp);

fscanf(stream,"%c",&c);

/*Output data read:*/

printf("%s\n",s);

printf("%ld\n",l);

printf("%f\n",fp);

printf("%c\n",c);

fclose(stream);

}

}

注意事项：

 fscanf(FILE * stream ,constchar*format, [argument...] );

如果argument为char* str时str是一个指向字符串数组的指针，用来拷贝读取到的字符串所以， 可以是 char s[128]也可以是 char* s = (char *)malloc(128)

但不可以是 char* s;  s没有指向有效的内存空间

FILE*fp;

char a[10];

int b;

double c;

fscanf(fp,"%s%d%lf",a,&b,&c)

printf("%g",4.5);//4.5printf("%f",4.5);//4.500000printf("%e",400.5);//4.5e+2