man3/euidaccess.3

   1 .\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\"
   3 .\" %%%LICENSE_START(VERBATIM)
   4 .\" Permission is granted to make and distribute verbatim copies of this
   5 .\" manual provided the copyright notice and this permission notice are
   6 .\" preserved on all copies.
   7 .\"
   8 .\" Permission is granted to copy and distribute modified versions of this
   9 .\" manual under the conditions for verbatim copying, provided that the
  10 .\" entire resulting derived work is distributed under the terms of a
  11 .\" permission notice identical to this one.
  12 .\"
  13 .\" Since the Linux kernel and libraries are constantly changing, this
  14 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
  15 .\" responsibility for errors or omissions, or for damages resulting from
  16 .\" the use of the information contained herein.  The author(s) may not
  17 .\" have taken the same level of care in the production of this manual,
  18 .\" which is licensed free of charge, as they might when working
  19 .\" professionally.
  20 .\"
  21 .\" Formatted or processed versions of this manual, if unaccompanied by
  22 .\" the source, must acknowledge the copyright and authors of this work.
  23 .\" %%%LICENSE_END
  24 .\"
  25 .TH EUIDACCESS 3 2017-09-15 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 euidaccess, eaccess \- check effective user's permissions for a file
  28 .SH SYNOPSIS
  29 .nf
  30 .BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
  31 .B #include <unistd.h>
  32 .PP
  33 .BI "int euidaccess(const char *" pathname ", int " mode );
  34 .BI "int eaccess(const char *" pathname ", int " mode );
  35 .fi
  36 .SH DESCRIPTION
  37 Like
  38 .BR access (2),
  39 .BR euidaccess ()
  40 checks permissions and existence of the file identified by its argument
  41 .IR pathname .
  42 However, whereas
  43 .BR access (2)
  44 performs checks using the real user and group identifiers of the process,
  45 .BR euidaccess ()
  46 uses the effective identifiers.
  47 .PP
  48 .I mode
  49 is a mask consisting of one or more of
  50 .BR R_OK ", " W_OK ", " X_OK ", and " F_OK ,
  51 with the same meanings as for
  52 .BR access (2).
  53 .PP
  54 .BR eaccess ()
  55 is a synonym for
  56 .BR euidaccess (),
  57 provided for compatibility with some other systems.
  58 .SH RETURN VALUE
  59 On success (all requested permissions granted), zero is returned.
  60 On error (at least one bit in
  61 .I mode
  62 asked for a permission that is denied, or some other error occurred),
  63 \-1 is returned, and
  64 .I errno
  65 is set appropriately.
  66 .SH ERRORS
  67 As for
  68 .BR access (2).
  69 .SH VERSIONS
  70 The
  71 .BR eaccess ()
  72 function was added to glibc in version 2.4.
  73 .SH ATTRIBUTES
  74 For an explanation of the terms used in this section, see
  75 .BR attributes (7).
  76 .TS
  77 allbox;
  78 lbw23 lb lb
  79 l l l.
  80 Interface       Attribute       Value
  81 T{
  82 .BR euidaccess (),
  83 .BR eaccess ()
  84 T}      Thread safety   MT-Safe
  85 .TE
  86 .SH CONFORMING TO
  87 These functions are nonstandard.
  88 Some other systems have an
  89 .\" e.g., FreeBSD 6.1.
  90 .BR eaccess ()
  91 function.
  92 .SH NOTES
  93 .IR Warning :
  94 Using this function to check a process's permissions on a file before
  95 performing some operation based on that information leads to race conditions:
  96 the file permissions may change between the two steps.
  97 Generally, it is safer just to attempt the desired operation and handle
  98 any permission error that occurs.
  99 .PP
 100 This function always dereferences symbolic links.
 101 If you need to check the permissions on a symbolic link, use
 102 .BR faccessat (2)
 103 with the flags
 104 .BR AT_EACCESS
 105 and
 106 .BR AT_SYMLINK_NOFOLLOW .
 107 .SH SEE ALSO
 108 .BR access (2),
 109 .BR chmod (2),
 110 .BR chown (2),
 111 .BR faccessat (2),
 112 .BR open (2),
 113 .BR setgid (2),
 114 .BR setuid (2),
 115 .BR stat (2),
 116 .BR credentials (7),
 117 .BR path_resolution (7)