C语言中文件的读/写结构-yiteyi-C++库

先决条件： C中的结构对于在文件中写入，使用 格式化输出 和 putc ，但在编写struct的内容时可能会遇到困难。 写入文件 和 弗雷德 当您想要写入和读取数据块时，使任务更容易。

null

写下： 下面是fwrite函数的声明

size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)ptr - This is pointer to array of elements to be writtensize -  This is the size in bytes of each element to be writtennmemb - This is the number of elements, each one with a size of size bytesstream - This is the pointer to a FILE object that specifies an output stream

C

                         // C program for writing                       
                         // struct to file                       
                         #include <stdio.h>                       
                         #include <stdlib.h>                       
                         #include <string.h>                       
           
                         // a struct to read and write                       
                         struct                                     person                       
                         {                       
                                                 int                                     id;                       
                                                 char                                     fname[20];                       
                                                 char                                     lname[20];                       
                         };                       
           
                         int                                     main ()                       
                         {                       
                                                 FILE                                     *outfile;                       
                                   
                                                 // open file for writing                       
                                                 outfile =                                     fopen                                     (                                     "person.dat"                                     ,                                     "w"                                     );                       
                                                 if                                     (outfile == NULL)                       
                                                 {                       
                                                 fprintf                                     (stderr,                                     "Error opened file"                                     );                       
                                                 exit                                     (1);                       
                                                 }                       
           
                                                 struct                                     person input1 = {1,                                     "rohan"                                     ,                                     "sharma"                                     };                       
                                                 struct                                     person input2 = {2,                                     "mahendra"                                     ,                                     "dhoni"                                     };                       
                                   
                                                 // write struct to file                       
                                                 fwrite                                     (&input1,                                     sizeof                                     (                                     struct                                     person), 1, outfile);                       
                                                 fwrite                                     (&input2,                                     sizeof                                     (                                     struct                                     person), 1, outfile);                       
                                   
                                                 if                                     (                                     fwrite                                     != 0)                       
                                                 printf                                     (                                     "contents to file written successfully !"                                     );                       
                                                 else                       
                                                 printf                                     (                                     "error writing file !"                                     );                       
           
                                                 // close file                       
                                                 fclose                                     (outfile);                       
           
                                                 return                                     0;                       
                         }                       

输出：

gcc demowrite.c./a.outcontents to file written successfully!

弗雷德： 下面是fread函数的声明

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)ptr - This is the pointer to a block of memory with a minimum size of size*nmemb bytes.size - This is the size in bytes of each element to be read.nmemb - This is the number of elements, each one with a size of size bytes.stream - This is the pointer to a FILE object that specifies an input stream.

C

                         // C program for reading                       
                         // struct from a file                       
                         #include <stdio.h>                       
                         #include <stdlib.h>                       
           
                         // struct person with 3 fields                       
                         struct                                     person                       
                         {                       
                                                 int                                     id;                       
                                                 char                                     fname[20];                       
                                                 char                                     lname[20];                       
                         };                       
           
                         // Driver program                       
                         int                                     main ()                       
                         {                       
                                                 FILE                                     *infile;                       
                                                 struct                                     person input;                       
                                   
                                                 // Open person.dat for reading                       
                                                 infile =                                     fopen                                     (                                     "person.dat"                                     ,                                     "r"                                     );                       
                                                 if                                     (infile == NULL)                       
                                                 {                       
                                                 fprintf                                     (stderr,                                     "Error opening file"                                     );                       
                                                 exit                                     (1);                       
                                                 }                       
                                   
                                                 // read file contents till end of file                       
                                                 while                                     (                                     fread                                     (&input,                                     sizeof                                     (                                     struct                                     person), 1, infile))                       
                                                 printf                                     (                                     "id = %d name = %s %s"                                     , input.id,                       
                                                 input.fname, input.lname);                       
           
                                                 // close file                       
                                                 fclose                                     (infile);                       
           
                                                 return                                     0;                       
                         }                       

输出：

gcc demoread.c./a.outid = 1   name = rohan sharmaid = 2   name = mahendra dhoni

本文由 曼迪星 .如果你喜欢GeekSforgek，并想贡献自己的力量，你也可以使用写极客。组织或者把你的文章寄去评论-team@geeksforgeeks.org.看到你的文章出现在Geeksforgeks主页上，并帮助其他极客。如果您发现任何不正确的地方，或者您想分享有关上述主题的更多信息，请写下评论。

文章版权归作者所有，未经允许请勿转载。

THE END