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access, _waccess

Header File

io.h

Category

Input/output Routines

Prototype

int access(const char *filename, int amode);

int _waccess(const wchar_t *filename, int amode);

Description

Determines accessibility of a file.

access checks the file named by filename to determine if it exists, and whether it can be read, written to, or executed.

The list of amode values is as follows:

06 | Check for read and write permission
04 | Check for read permission
02 | Check for write permission
01 | Execute (ignored)
00 | Check for existence of file

All existing files have read access (amode equals 04), so 00 and 04 give the same result. Similarly, amode values of 06 and 02 are equivalent because under Win32 write access implies read access.

If filename refers to a directory, access simply determines whether the directory exists.

Return Value

If the requested access is allowed, access returns 0; otherwise, it returns a value of -1, and the global variable errno is set to one of the following values:

ENOENT | Path or file name not found
EACCES | Permission denied

Example

Copy Code

     #include <stdio.h>
     #include <io.h>
     int file_exists(char *filename);
     int main(void)
     {
    printf("Does NOTEXIST.FIL exist: %s\n",
     file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
    return 0;
     }
     int file_exists(char *filename)
     {
       return (access(filename, 0) == 0);
     }

Portability

| POSIX | Win32 | ANSI C | ANSI C++
access | + | + |  |
_waccess |  | NT only |  |

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