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     access, eaccess - check accessibility of a file


     Standard C Library (libc, -lc)


     #include <unistd.h>

     access(const char *path, int mode);

     eaccess(const char *path, int mode);


     The access() and eaccess() system calls check the accessibility of the
     file named by the path argument for the access permissions indicated by
     the mode argument.  The value of mode is either the bitwise-inclusive OR
     of the access permissions to be checked (R_OK for read permission, W_OK
     for write permission, and X_OK for execute/search permission), or the
     existence test (F_OK).

     For additional information, see the File Access Permission section of

     The eaccess() system call uses the effective user ID and the group access
     list to authorize the request; the access() system call uses the real
     user ID in place of the effective user ID, the real group ID in place of
     the effective group ID, and the rest of the group access list.

     Even if a process’s real or effective user has appropriate privileges and
     indicates success for X_OK, the file may not actually have execute
     permission bits set.  Likewise for R_OK and W_OK.


     Upon successful completion, the value 0 is returned; otherwise the
     value -1 is returned and the global variable errno is set to indicate the


     Access to the file is denied if:

     [ENOTDIR]          A component of the path prefix is not a directory.

     [ENAMETOOLONG]     A component of a pathname exceeded 255 characters, or
                        an entire path name exceeded 1023 characters.

     [ENOENT]           The named file does not exist.

     [ELOOP]            Too many symbolic links were encountered in
                        translating the pathname.

     [EROFS]            Write access is requested for a file on a read-only
                        file system.

     [ETXTBSY]          Write access is requested for a pure procedure (shared
                        text) file presently being executed.

     [EACCES]           Permission bits of the file mode do not permit the
                        requested access, or search permission is denied on a
                        component of the path prefix.

     [EFAULT]           The path argument points outside the process’s
                        allocated address space.

     [EIO]              An I/O error occurred while reading from or writing to
                        the file system.


     The access() system call is a potential security hole due to race
     conditions and should never be used.  Set-user-ID and set-group-ID
     applications should restore the effective user or group ID, and perform
     actions directly rather than use access() to simulate access checks for
     the real user or group ID.  The eaccess() system call likewise may be
     subject to races if used inappropriately.


     chmod(2), intro(2), stat(2)


     The access() system call is expected to conform to ISO/IEC 9945-1:1990


     The access() function appeared in Version 7 AT&T UNIX.