C語言庫函數名: 簡介 函數原型： size_t fread(void *buffer, size_t size, size_tcount, FILE *stream); 功 能： 從一個文件流中讀數據,讀取count個元素,每個元素size字節.如果調用成功返回count.如果調用成功則實際讀取size*count字節 參 數： buffer 用於接收數據的內存地址,大小至少是size*count 字節. size 單個元素的大小，單位是字節 count 元素的個數,每個元素是size字節. stream 輸入流 返回值： 實際讀取的元素數.如果返回值與count(不是count*size)不相同,則可能文件結尾或發生錯誤. 從ferror和feof獲取錯誤信息或檢測是否到達文件結尾. 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" ); }
