fread,fwrite ,fscanf,fprintf 使用

函数名: fread 
功  能: 从一个流中读数据 
用  法: int fread(void *ptr, int size, int nitems, FILE *stream); 
程序例: 

#include <string.h> 
#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 
   char msg[] = "this is a test"; 
   char buf[20]; 

   if ((stream = fopen("DUMMY.FIL", "w+")) 
       == NULL) 
   { 
      fprintf(stderr, 
              "Cannot open output file.\n"); 
      return 1; 
   } 

   /* write some data to the file */ 
   fwrite(msg, strlen(msg)+1, 1, stream); 

   /* seek to the beginning of the file */ 
   fseek(stream, SEEK_SET, 0); 

   /* read the data and display it */ 
   fread(buf, strlen(msg)+1, 1, stream); 
   printf("%s\n", buf); 

   fclose(stream); 
   return 0; 
} 

  

C/C++ code

函数名: fwrite 
功  能: 写内容到流中 
用  法: int fwrite(void *ptr, int size, int nitems, FILE *stream); 
程序例: 

#include <stdio.h> 

struct mystruct 
{ 
  int i; 
  char ch; 
}; 

int main(void) 
{ 
   FILE *stream; 
   struct mystruct s; 

   if ((stream = fopen("TEST.$$$", "wb")) == NULL) /* open file TEST.$$$ */ 
   { 
      fprintf(stderr, "Cannot open output file.\n"); 
      return 1; 
   } 
   s.i = 0; 
   s.ch = 'A'; 
   fwrite(&s, sizeof(s), 1, stream); /* write struct s to file */ 
   fclose(stream); /* close file */ 
   return 0; 
} 

函数名: fscanf 
功  能: 从一个流中执行格式化输入 
用  法: int fscanf(FILE *stream, char *format[,argument...]); 
程序例: 

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

int main(void) 
{ 
   int i; 

   printf("Input an integer: "); 

   /* read an integer from the 
      standard input stream */ 
   if (fscanf(stdin, "%d", &i)) 
      printf("The integer read was: %i\n", 
             i); 
   else 
   { 
      fprintf(stderr, "Error reading an \ 
              integer from stdin.\n"); 
      exit(1); 
   } 
   return 0; 
} 
  

C/C++ code

函数名: fprintf 
功  能: 传送格式化输出到一个流中 
用  法: int fprintf(FILE *stream, char *format[, argument,...]); 
程序例: 

/* Program to create backup of the 
   AUTOEXEC.BAT file */ 

#include <stdio.h> 

int main(void) 
{ 
   FILE *in, *out; 

   if ((in = fopen("\\AUTOEXEC.BAT", "rt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open input \ 
       file.\n"); 
      return 1; 
   } 

   if ((out = fopen("\\AUTOEXEC.BAK", "wt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open output \ 
       file.\n"); 
      return 1; 
   } 

   while (!feof(in)) 
      fputc(fgetc(in), out); 

   fclose(in); 
   fclose(out); 
   return 0; 
}