bsd/man/man2/access.2

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  34 .\"     @(#)access.2    8.2 (Berkeley) 4/1/94
  35 .\"
  36 .Dd April 1, 1994
  37 .Dt ACCESS 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm access
  41 .Nd check access permissions of a file or pathname
  42 .Sh SYNOPSIS
  43 .Fd #include <unistd.h>
  44 .Ft int
  45 .Fn access "const char *path" "int mode"
  46 .Sh DESCRIPTION
  47 The
  48 .Fn access
  49 function checks the accessibility of the
  50 file named by
  51 .Fa path
  52 for the access permissions indicated by
  53 .Fa mode .
  54 The value of
  55 .Fa mode
  56 is the bitwise inclusive OR of the access permissions to be
  57 checked
  58 .Pf ( Dv R_OK
  59 for read permission,
  60 .Dv W_OK
  61 for write permission and
  62 .Dv X_OK
  63 for execute/search permission) or the existence test,
  64 .Dv F_OK .
  65 All components of the pathname
  66 .Fa path
  67 are checked for access permissions (including
  68 .Dv F_OK ) .
  69 .Pp
  70 The real user ID is used in place of the effective user ID
  71 and the real group access list
  72 (including the real group ID) are
  73 used in place of the effective ID for verifying permission.
  74 .Pp
  75 Even if a process has appropriate privileges and indicates success for
  76 .Dv X_OK ,
  77 the file may not actually have execute permission bits set.
  78 Likewise for
  79 .Dv R_OK
  80 and
  81 .Dv W_OK .
  82 .Sh RETURN VALUES
  83 If
  84 .Fa path
  85 cannot be found or if any of the desired access modes would
  86 not be granted, then a -1 value is returned; otherwise
  87 a 0 value is returned.
  88 .Sh ERRORS
  89 Access to the file is denied if:
  90 .Bl -tag -width Er
  91 .It Bq Er ENOTDIR
  92 A component of the path prefix is not a directory.
  93 .It Bq Er ENAMETOOLONG
  94 A component of a pathname exceeded
  95 .Dv {NAME_MAX}
  96 characters, or an entire path name exceeded
  97 .Dv {PATH_MAX}
  98 characters.
  99 .It Bq Er ENOENT
 100 The named file does not exist.
 101 .It Bq Er ELOOP
 102 Too many symbolic links were encountered in translating the pathname.
 103 .It Bq Er EROFS
 104 Write access is requested for a file on a read-only file system.
 105 .It Bq Er ETXTBSY
 106 Write access is requested for a pure procedure (shared text)
 107 file presently being executed.
 108 .It Bq Er EACCES
 109 Permission bits of the file mode do not permit the requested
 110 access, or search permission is denied on a component of the
 111 path prefix.  The owner of a file has permission checked with
 112 respect to the ``owner'' read, write, and execute mode bits,
 113 members of the file's group other than the owner have permission
 114 checked with respect to the ``group'' mode bits, and all
 115 others have permissions checked with respect to the ``other''
 116 mode bits.
 117 .It Bq Er EFAULT
 118 .Fa Path
 119 points outside the process's allocated address space.
 120 .It Bq Er EIO
 121 An I/O error occurred while reading from or writing to the file system.
 122 .It Bq Er EINVAL
 123 An invalid value was specified for
 124 .Ar mode .
 125 .El
 126 .Sh SEE ALSO
 127 .Xr chmod 2 ,
 128 .Xr stat 2
 129 .Sh STANDARDS
 130 The
 131 .Fn access
 132 function conforms to
 133 .St -p1003.1-90 .
 134 .Sh CAVEAT
 135 .Fn Access
 136 is a potential security hole and
 137 should never be used.