[SOLVED] warning: implicit declaration of function

[jordanmthomas]

I'm writing a shell for a school assignment in c, and it has to compile without any warnings. To get the current directory, I am using get_current_dir_name.

Here's what I think is the relevant code (snipped up for clarity):
#include <unistd.h>
int main(int argc, char** argv)
{
char* cwd = (char*)get_current_dir_name();
}

When I compile, this warning is given:

jshell.c:19: warning: implicit declaration of function ‘get_current_dir_name’

I don't understand why this is happening because according to man get_current_dir_name, I should just have to include unistd.h

man get_current_dir_name
...SYNOPSIS
#include <unistd.h>
...
...
char *get_current_dir_name(void);


The code works fine, but I don't know how to get rid of the warning. Any help is appreciated. I'm sure it's something stupid on my part, but I can't figure it out.

Thanks in advance.

**edit** This warning doesn't come up if I don't use -Wall when compiling, but I am required to use it :).
**edit2** Using other functions from unistd.h does not result in the warning.

[Wybiral]

#define _GNU_SOURCE
#include <unistd.h>
int main(int argc, char** argv)
{
char* cwd = (char*)get_current_dir_name();
}


Man page: "get_current_dir_name(), which is only prototyped if _GNU_SOURCE is defined"

You should probably stick with "getcwd" though.


#include <stdio.h>
#include <unistd.h>

int main(int argc, char** argv)
{
char my_cwd[1024];
getcwd(my_cwd, 1024);
printf("%s\n", my_cwd);
return 0;
}

[jordanmthomas]

Aha! Thanks a lot.

[jordanmthomas]

Well, almost got it. It doesn't say that in my manpage anywhere, but at least I have a hunch. I'm sure I'll get it figured out now though.

[Wybiral]

Well, almost got it. It doesn't say that in my manpage anywhere, but at least I have a hunch. I'm sure I'll get it figured out now though.

I read it from: http://linux.die.net/man/3/get_current_dir_name (I thought it was a replica of the normal man pages, must not be).

But like I said, getcwd it more commonly used, so if you can use it, you should.

[jordanmthomas]

OK, I have switched over to getcwd and no more errors.
I guess the warning was related to _GNU_SOURCE like you said, but maybe my system's a little screwy or something.

Thanks again for the help