错误：未知类型名称'FILE' [英] error: unknown type name ‘FILE’

问题描述

我正在制作一个函数，只是将hello写入文件。我把它放在一个不同的文件中，并将它的头文件包含在程序中。但gcc发出错误，即：错误：未知类型名称'FILE'。
代码如下：

app.c：

 ＃包括< stdio.h中> 
＃include< stdlib.h> 
 #includewrite_hello.h
 
 int main（）{
 FILE * fp; 
 fp = fopen（new_file.txt，w）; 
 
 write_hello（fp）; 
 
返回0; 
} 
  

write_hello.h：

  void write_hello（FILE *）; 
  

write_hello.c：

  void write_hello（FILE * fp）{
 fprintf（fp，hello）; 
 printf（Done \\\
）; 
} 
  

当由gcc编译时，会发生以下情况：

  harsh @ harsh-Inspiron-3558：〜/ c / bank_management / include / test $ sudo gcc app.c 
 write_hello.c -o app 
 write_hello.c：3：18：error：unknown type name'FILE'
 void write_hello（FILE * fp）{
 ^ 
  

对不起，有任何错误。我是初学者。

解决方案

FILE在stdio.h中定义，您需要将其包含在每个使用它的文件中。所以write_hello.h和write_hello.c都应该包含它，write_hello.c也应该包含write_hello.h（因为它实现了write_hello.h中定义的函数）。

还要注意，每个头文件的标准做法是定义一个名称相同的宏（IN CAPS），并在#ifndef，#endif之间包含整个头文件。在C中，这可以防止头部获得#included两次。这被称为内部包含警卫（感谢Story Teller指出）。

write_hello.h

  #ifndef WRITE_HELLO_H 
 #define WRITE_HELLO_H 
 #include< stdio.h> 
 void write_hello（FILE *）; 
 #endif 
  

write_hello.c

  #include  
 #includewrite_hello.h
 void write_hello（FILE * fp）{
 fprintf（fp，hello）; 
 printf（Done \\\
）; 
} 
  

I am making a function which is just writes "hello" to a file. I have put it in a different file and included its header in the program.But gcc is giving an error namely: error: unknown type name ‘FILE’. The code is given below

app.c:

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

int main(){
    FILE* fp;
    fp = fopen("new_file.txt","w");

    write_hello(fp);

    return 0;
}

write_hello.h:

void write_hello(FILE*);

write_hello.c:

void write_hello(FILE* fp){
    fprintf(fp,"hello");
    printf("Done\n");
}

when compiling by gcc the following occurs:

harsh@harsh-Inspiron-3558:~/c/bank_management/include/test$ sudo gcc app.c 
write_hello.c -o app
write_hello.c:3:18: error: unknown type name ‘FILE’
 void write_hello(FILE* fp){
                  ^

Sorry for any mistakes.I am a beginner.

解决方案

FILE is defined in stdio.h and you need to include it in each file that uses it. So write_hello.h and write_hello.c should both include it, and write_hello.c should also include write_hello.h (since it implements the function defined in write_hello.h).

Also note that it is standard practice for every header file to define a macro of the same name (IN CAPS), and enclose the entire header between #ifndef, #endif. In C, this prevents a header from getting #included twice. This is known as the "internal include guard" (with thanks to Story Teller for pointing that out).

write_hello.h

#ifndef WRITE_HELLO_H
#define WRITE_HELLO_H
#include <stdio.h>
void write_hello(FILE*);
#endif

write_hello.c

#include <stdio.h>
#include "write_hello.h"
void write_hello(FILE* fp){
    fprintf(fp,"hello");
    printf("Done\n");
}

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