What is wrong with this header file?

Question

I'm fairly new to C and am starting to learn header files. Whilst using my header I'm getting an error saying invalid type argument of '->' (have struct dirent). I don't understand what this means, I read here that the second argument to -> must be a pointer, so I tried to add a * to it (ent->*d_name) however then I get the error unexpected token *, how can I fix this?

#ifndef UTILIS_H_INCLUDED
#define UTILIS_H_INCLUDED "utilis.h"
#include <stdio.h>
#include <dirent.h>

char *connect(const char *pattern)
{
    struct dirent ent;
    char *d_name;

    DIR *mgt = opendir("\\\\example\\windows7apps");

    while ((ent = readdir(mgt)) != pattern)
    {
        puts(ent->d_name);
    }
}

#endif

You might want to read e.g. [this `readdir` manual page](http://man7.org/linux/man-pages/man3/readdir.3.html). What does `readdir` return? What is the type of `ent`? — Some programmer dude, Apr 07 '17 at 12:50
If this is a header, you most definitely don't want the entire function definition in here. Either move it to a .c file or mark it as `inline`. — DeiDei, Apr 07 '17 at 13:11

Sourav Ghosh · Accepted Answer · 2017-04-07T13:47:43.790

3

I read here that the second argument to -> must be a pointer,

That's wrong, the "first" argument, or, actually, the operand of the -> operator should be of pointer type.

In your case, ent is not a pointer type, so you cannot use the pointer member dereference operator ->. (you could have used the member dereference operator . instead).

Actually, in your code, ent should be a pointer, as per the return type of readdir(). So you better correct the type of ent to be of struct dirent *, then you can make use of -> on ent.

edited Apr 07 '17 at 13:47

answered Apr 07 '17 at 12:50

Sourav Ghosh

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So `ent.d_name`? – jakehimton Apr 07 '17 at 12:52

score 3 · Answer 2 · answered Apr 07 '17 at 12:53

usually header files only contain data definitions and function prototypes. Your function definition should almost certainly be in a C file.

If you look at the function readdir it returns a pointer to a struct dirent so your variable ent should be a pointer struct dirent *readdir(DIR *dirp);

struct dirent *ent;

That will fix your error invalid type argument of '->' (have struct dirent)

What is wrong with this header file?

2 Answers2