bsd/man/man2/access.2

   1 .\"     $NetBSD: access.2,v 1.7 1995/02/27 12:31:44 cgd Exp $
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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 .Fo access
  46 .Fa "const char *path"
  47 .Fa "int amode"
  48 .Fc
  49 .Sh DESCRIPTION
  50 The
  51 .Fn access
  52 function checks the accessibility of the
  53 file named by
  54 .Fa path
  55 for the access permissions indicated by
  56 .Fa amode .
  57 The value of
  58 .Fa amode
  59 is the bitwise inclusive OR of the access permissions to be
  60 checked
  61 .Pf ( Dv R_OK
  62 for read permission,
  63 .Dv W_OK
  64 for write permission and
  65 .Dv X_OK
  66 for execute/search permission) or the existence test,
  67 .Dv F_OK .
  68 All components of the pathname
  69 .Fa path
  70 are checked for access permissions (including
  71 .Dv F_OK ) .
  72 .Pp
  73 The real user ID is used in place of the effective user ID
  74 and the real group access list
  75 (including the real group ID) are
  76 used in place of the effective ID for verifying permission.
  77 .Pp
  78 Even if a process has appropriate privileges and indicates success for
  79 .Dv X_OK ,
  80 the file may not actually have execute permission bits set.
  81 Likewise for
  82 .Dv R_OK
  83 and
  84 .Dv W_OK .
  85 .Sh RETURN VALUES
  86 If
  87 .Fa path
  88 cannot be found
  89 or if any of the desired access modes would not be granted,
  90 then a -1 value is returned and the global integer variable
  91 .Va errno
  92 is set to indicate the error.
  93 Otherwise, a 0 value is returned.
  94 .Sh ERRORS
  95 Access to the file is denied if:
  96 .Bl -tag -width Er
  97 .\" ==========
  98 .It Bq Er EACCES
  99 Permission bits of the file mode do not permit the requested access,
 100 or search permission is denied on a component of the path prefix.
 101 .Pp
 102 The owner of a file has permission checked
 103 with respect to the ``owner'' read, write, and execute mode bits,
 104 members of the file's group other than the owner have permission checked
 105 with respect to the ``group'' mode bits,
 106 and all others have permissions checked
 107 with respect to the ``other'' mode bits.
 108 .\"
 109 .\" ==========
 110 .It Bq Er EFAULT
 111 .Fa Path
 112 points outside the process's allocated address space.
 113 .It Bq Er EINVAL
 114 An invalid value was specified for
 115 .Ar amode .
 116 .\" ==========
 117 .It Bq Er EIO
 118 An I/O error occurred while reading from or writing to the file system.
 119 .\" ==========
 120 .It Bq Er ELOOP
 121 Too many symbolic links were encountered in translating the pathname.
 122 .\" ==========
 123 .It Bq Er ENAMETOOLONG
 124 A component of a pathname exceeded
 125 .Dv {NAME_MAX}
 126 characters, or an entire path name exceeded
 127 .Dv {PATH_MAX}
 128 characters.
 129 .\" ==========
 130 .It Bq Er ENOENT
 131 The named file does not exist.
 132 .\" ==========
 133 .It Bq Er ENOTDIR
 134 A component of the path prefix is not a directory.
 135 .\" ==========
 136 .It Bq Er EROFS
 137 Write access is requested for a file on a read-only file system.
 138 .\" ==========
 139 .It Bq Er ETXTBSY
 140 Write access is requested for a pure procedure (shared text)
 141 file that is presently being executed.
 142 .El
 143 .Sh SEE ALSO
 144 .Xr chmod 2 ,
 145 .Xr stat 2
 146 .Sh STANDARDS
 147 The
 148 .Fn access
 149 function conforms to
 150 .St -p1003.1-90 .
 151 .Sh CAVEAT
 152 .Fn Access
 153 is a potential security hole and
 154 should never be used.