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access(2)

NAME

     access, eaccess -- check accessibility of a file

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     access(const char *path, int mode);

     int
     eaccess(const char *path, int mode);

DESCRIPTION

     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
     intro(2).

     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 per-
     mission bits set.	Likewise for R_OK and W_OK.

RETURN VALUES

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

ERRORS

     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 translat-
			ing 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

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

SECURITY CONSIDERATIONS

     The access() system call is a potential security hole due to race condi-
     tions and should never be used.  Set-user-ID and set-group-ID applica-
     tions 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.

SEE ALSO

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

STANDARDS

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

HISTORY

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

FreeBSD 5.4		      September 21, 2001		   FreeBSD 5.4

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