fread
转自：http://baike.baidu.com/view/656689.htm
目录
- C语言库函数名:
- 展开
编辑本段C语言库函数名:
简介
函数原型：
size_t fread(void *buffer, size_t size, size_t count, FILE *stream);
功 能：
从一个文件流中读数据,读取count个元素,每个元素size字节.如果调用成功返回count.返回实际读取size*count字节.如不成功，返回实际读取的元素个数
参 数：
buffer
用于接收数据的内存地址,大小至少是 size * count 字节.
size
单个元素的大小，单位是字节
count
元素的个数,每个元素是size字节.
stream
输入流，被读取的文件
返回值：
实际读取的元素数.如果返回值与count(不是count*size)不相同,则可能文件结尾或发生错误.
从ferror和feof获取错误信息或检测是否到达文件结尾.
程序例
#include <stdio.h>
#include <string.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, 1,strlen(msg)+1, stream); /* seek to the beginning of the file */
fseek(stream, 0, SEEK_SET); /* read the data and display it */
fread(buf, 1,strlen(msg)+1,stream);
printf("%s\n", buf);
fclose(stream);
return 0;
}
MSDN示例
#include <stdio.h>
void main( void )
{
FILE *stream;
char list[30];
int i, numread, numwritten; /* Open file in text mode: */
if( (stream = fopen( "fread.out", "w+t" )) != NULL )
{
for ( i = 0; i < 25; i++ )
list[i] = (char)('z' - i); /* Write 25 characters to stream */
numwritten = fwrite( list, sizeof( char ), 25, stream );
printf( "Wrote %d items\n", numwritten );
fclose( stream );
}
else
printf( "Problem opening the file\n" );
if( (stream = fopen( "fread.out", "r+t" )) != NULL )
{ /* Attempt to read in 25 characters */
numread = fread( list, sizeof( char ), 25, stream );
printf( "Number of items read = %d\n", numread );
printf( "Contents of buffer = %.25s\n", list );
fclose( stream );
}
else
printf( "File could not be opened\n" );
}
