Checking if a file is a directory or just a file [

问题:

This question already has answers here:

Checking if a directory exists in Unix (system call) (4 answers)

Closed 4 years ago.

I'm writing a program to check if something is a file or is a directory. Is there a better way to do it than this?

#include <stdio.h>

#include <sys/types.h>
#include <dirent.h>
#include <errno.h>

int isFile(const char* name)
{
    DIR* directory = opendir(name);

    if(directory != NULL)
    {
     closedir(directory);
     return 0;
    }

    if(errno == ENOTDIR)
    {
     return 1;
    }

    return -1;
}

int main(void)
{
    const char* file = "./testFile";
    const char* directory = "./";

    printf("Is %s a file? %s.\n", file,
     ((isFile(file) == 1) ? "Yes" : "No"));

    printf("Is %s a directory? %s.\n", directory,
     ((isFile(directory) == 0) ? "Yes" : "No"));

    return 0;
}

回答1:

You can call the stat() function and use the S_ISREG() macro on the st_mode field of the stat structure in order to determine if your path points to a regular file:

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

int is_regular_file(const char *path)
{
    struct stat path_stat;
    stat(path, &path_stat);
    return S_ISREG(path_stat.st_mode);
}

Note that there are other file types besides regular and directory, like devices, pipes, symbolic links, sockets, etc. You might want to take those into account.

回答2:

Use the S_ISDIRmacro:

int isDirectory(const char *path) {
   struct stat statbuf;
   if (stat(path, &statbuf) != 0)
       return 0;
   return S_ISDIR(statbuf.st_mode);
}

回答3:

Yes, there is better. Check the stat or the fstat function

回答4:

Normally you want to perform this check atomically with using the result, so stat() is useless. Instead, open() the file read-only first and use fstat(). If it's a directory, you can then use fdopendir() to read it. Or you can try opening it for writing to begin with, and the open will fail if it's a directory. Some systems (POSIX 2008, Linux) also have an O_DIRECTORY extension to open which makes the call fail if the name is not a directory.

Your method with opendir() is also good if you want a directory, but you should not close it afterwards; you should go ahead and use it.