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

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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.

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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");
        }
}

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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");
        }       
}

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#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().

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