man2/faccessat.2

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  26 .TH FACCESSAT 2 2007-02-28 "Linux 2.6.16" "Linux Programmer's Manual"
  27 .SH NAME
  28 faccessat \- check user's permissions of a file relative to a \
  29 directory file descriptor
  30 .SH SYNOPSIS
  31 .nf
  32 .B #define _ATFILE_SOURCE
  33 .B #include <fcntl.h>
  34 .B #include <unistd.h>
  35 .sp
  36 .BI "int faccessat(int " dirfd ", const char *" pathname ", int " \
  37 mode ", int " flags );
  38 .fi
  39 .SH DESCRIPTION
  40 The
  41 .BR faccessat ()
  42 system call operates in exactly the same way as
  43 .BR access (2),
  44 except for the differences described in this manual page.
  45
  46 If the pathname given in
  47 .I pathname
  48 is relative, then it is interpreted relative to the directory
  49 referred to by the file descriptor
  50 .IR dirfd
  51 (rather than relative to the current working directory of
  52 the calling process, as is done by
  53 .BR access (2)
  54 for a relative pathname).
  55
  56 If
  57 .I pathname
  58 is relative and
  59 .I dirfd
  60 is the special value
  61 .BR AT_FDCWD ,
  62 then
  63 .I pathname
  64 is interpreted relative to the current working
  65 directory of the calling process (like
  66 .BR access (2)).
  67
  68 If
  69 .IR pathname
  70 is absolute, then
  71 .I dirfd
  72 is ignored.
  73
  74 .I flags
  75 is constructed by ORing together zero or more of the following values:
  76 .TP
  77 .B AT_EACCESS
  78 Perform access checks using the effective user and group IDs.
  79 By default,
  80 .BR faccessat ()
  81 uses the real IDs (like
  82 .BR access (2)).
  83 .TP
  84 .B AT_SYMLINK_NOFOLLOW
  85 If
  86 .I pathname
  87 is a symbolic link, do not dereference it:
  88 instead return information about the link itself.
  89 .SH "RETURN VALUE"
  90 On success, (all requested permissions granted)
  91 .BR faccessat ()
  92 returns 0.
  93 On error, \-1 is returned and
  94 .I errno
  95 is set to indicate the error.
  96 .SH ERRORS
  97 The same errors that occur for
  98 .BR access (2)
  99 can also occur for
 100 .BR faccessat ().
 101 The following additional errors can occur for
 102 .BR faccessat ():
 103 .TP
 104 .B EBADF
 105 .I dirfd
 106 is not a valid file descriptor.
 107 .TP
 108 .B EINVAL
 109 Invalid flag specified in
 110 .IR flags .
 111 .TP
 112 .B ENOTDIR
 113 .I pathname
 114 is relative and
 115 .I dirfd
 116 is a file descriptor referring to a file other than a directory.
 117 .SH NOTES
 118 See
 119 .BR openat (2)
 120 for an explanation of the need for
 121 .BR faccessat ().
 122 .SS Glibc Notes
 123 The
 124 .B AT_EACCESS
 125 and
 126 .B AT_SYMLINK_NOFOLLOW
 127 flags are actually implemented within the glibc wrapper function for
 128 .BR faccessat ().
 129 If either of these flags are specified, then the wrapper function employs
 130 .BR fstatat (2)
 131 to determine access permissions.
 132 .SH VERSIONS
 133 .BR faccessat ()
 134 was added to Linux in kernel 2.6.16.
 135 .SH "CONFORMING TO"
 136 This system call is non-standard but is proposed
 137 for inclusion in a future revision of POSIX.1.
 138 .SH "SEE ALSO"
 139 .BR access (2),
 140 .BR openat (2),
 141 .BR path_resolution (2),
 142 .BR eauidaccess (3)