Existence of a file given its path

Given the path, is ther开发者_C百科e a way to find out whether the file exists without opening the file?

Thanks

The most efficient way is access with the F_OK flag.

stat also works but it's much heavier weight since it has to read the inode contents, not just the directory.

You can use the stat system call. Make sure though that you check errno for the correct error because stat may return -1 for a number of other reasons/Failures.

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
main()
{
        struct stat BUF;
        if(stat("/Filepath/FileName",&BUF)==0)
        {
                printf("File exists\n");
        }
}

Another way is by using the access function.

#include <unistd.h>

main()
{
        if(access("/Filepath/FileName", F_OK) != -1 ) 
        {
               printf("File exists\n");
        } 
        else 
        {
               printf("File does not exist\n");
        }       
}

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

int rc;
struct stat mystat;
rc = stat(path, &mystat);

Now check rc and (maybe) errno.

EDIT 2011-09-18 addendum:

Both access() and stat() return 0 if the path points to a non-file (directory, fifo,symlink, whatever)

In the stat() case, this can be tested with "((st_mode & S_IFREG) == S_IFREG)". Best way still is to just try to open the file with open() or fopen().

Try to remove it (unlink()). If successful, it doesn't exist anymore. If unsuccessful, interpret errno to see if it exists :)