faccessat(2)

1FACCESSAT(2)               Linux Programmer's Manual              FACCESSAT(2)
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NAME

6       faccessat  - check user's permissions of a file relative to a directory
7       file descriptor
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SYNOPSIS

10       #define _ATFILE_SOURCE
11       #include <fcntl.h>
12       #include <unistd.h>
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14       int faccessat(int dirfd, const char *pathname, int mode, int flags);
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DESCRIPTION

17       The faccessat() system  call  operates  in  exactly  the  same  way  as
18       access(2), except for the differences described in this manual page.
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20       If  the  pathname given in pathname is relative, then it is interpreted
21       relative to the directory referred to  by  the  file  descriptor  dirfd
22       (rather  than  relative to the current working directory of the calling
23       process, as is done by access(2) for a relative pathname).
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25       If pathname is relative and dirfd is the special value  AT_FDCWD,  then
26       pathname  is  interpreted  relative to the current working directory of
27       the calling process (like access(2)).
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29       If pathname is absolute, then dirfd is ignored.
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31       flags is constructed by ORing together zero or more  of  the  following
32       values:
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34       AT_EACCESS
35              Perform  access  checks  using the effective user and group IDs.
36              By default, faccessat() uses the real IDs (like access(2)).
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38       AT_SYMLINK_NOFOLLOW
39              If pathname is a symbolic link, do not dereference  it:  instead
40              return information about the link itself.
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RETURN VALUE

43       On  success, (all requested permissions granted) faccessat() returns 0.
44       On error, -1 is returned and errno is set to indicate the error.
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ERRORS

47       The same errors that occur for access(2) can  also  occur  for  facces‐
48       sat().  The following additional errors can occur for faccessat():
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50       EBADF  dirfd is not a valid file descriptor.
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52       EINVAL Invalid flag specified in flags.
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54       ENOTDIR
55              pathname is relative and dirfd is a file descriptor referring to
56              a file other than a directory.
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NOTES

59       See openat(2) for an explanation of the need for faccessat().
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CONFORMING TO

62       This system call is non-standard but is proposed  for  inclusion  in  a
63       future revision of POSIX.1.
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GLIBC NOTES

66       The  AT_EACCESS  and AT_SYMLINK_NOFOLLOW flags are actually implemented
67       within the glibc wrapper function for faccessat().  If either of  these
68       flags  are  specified,  then the wrapper function employs fstatat(2) to
69       determine access permissions.
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VERSIONS

72       faccessat() was added to Linux in kernel 2.6.16.
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