File.exists in C?

[sitko]

Hi,

I'm a VB programmer, and was wondering, is there a way to check and see if a file exists in straight C?

In VB the code is:

File.Exists(strDir & "filename.txt") 'returns a boolean true if it exists, false if not
 

Thanks,
Sitko.

[sitko]

Hi,

I found this online:

bool file_exists(const char * filename)
{
    if (FILE * file == fopen(filename, "r"))
    {
        fclose(file);
        return true;
    }
    return false;
}
 

I didn't think bool existed in C, nor the usage of "true" and "false"

Is this a better version (to make it usable by all flavors of Unix?

int file_exists( char * filename)
{
    if (FILE * file == fopen(filename, "r"))
    {
        fclose(file);
        return 1;
    }
        else
    {
        return 0;
    }
}
 

Thanks,
Sitko

[sicarie]

Well, if you think about it, they do the same thing. 0 stands for a fail and any other number stands for a pass/true condition in a loop, so you're really just changing the datatype you're returning. I can't think of a specific reason one would work better than the other in Linux.

[sitko]

Well, if you think about it, they do the same thing. 0 stands for a fail and any other number stands for a pass/true condition in a loop, so you're really just changing the datatype you're returning. I can't think of a specific reason one would work better than the other in Linux.

I changed the "="s to "=="s, is that correct as well?

Thanks,
Sitko.

[sicarie]

I changed the "="s to "=="s, is that correct as well?

Thanks,
Sitko.

Well, let's think about that. You changed the conditional 'is equal to' == operator to the assignment '=' operator. So what happened to

if (FILE * file == fopen(filename, "r"))
 

when you changed that? Hint - what is fopen()? Does it have a return type?

[sitko]

Well, let's think about that. You changed the conditional 'is equal to' == operator to the assignment '=' operator. So what happened to

if (FILE * file == fopen(filename, "r"))
 

when you changed that? Hint - what is fopen()? Does it have a return type?

Yeah, I realized that it was bad to change that...and have set it back...

Now, I'm wondering is there a way to check if a directory exists?

Thanks,
Sitko.

[sicarie]

Just to clarify, you're doing this all in Linux, correct?

There are other ways to do this in Windows if you're using the Win32 API...

[sitko]

Yes, linux or another flavor of unix...trying convert some VB code to be able to run on Unix and Linux...

My current thinking (regarding checking to see if a directory exists), is to just make "system(); calls, with 'cd <dirName> as the argument...


Thanks,
Sitko.

[sicarie]

So I just did a really quick search (as I'm on my way out the door) - there is an exists() function for looking for files and directories in Linux, but I'm not sure what library it's in. But you can Google that, and if I get a chance later, I'll hop on and look. (Anyone else out there know of exists() in Linux and what lib it's in?)

[sitko]

I attempted to do a "man exists" on our unix and it says "no manual entry for exists"

Ideally, I want to make this as platform independent as possible...port ability is the goal here...

Thanks,
Sitko.