man3/dirfd.3

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  25 .TH DIRFD 3 2016-03-15 "Linux" "Linux Programmer's Manual"
  26 .SH NAME
  27 dirfd \- get directory stream file descriptor
  28 .SH SYNOPSIS
  29 .B #include <sys/types.h>
  30 .br
  31 .B #include <dirent.h>
  32 .sp
  33 .BI "int dirfd(DIR *" dirp );
  34 .sp
  35 .in -4n
  36 Feature Test Macro Requirements for glibc (see
  37 .BR feature_test_macros (7)):
  38 .in
  39 .sp
  40 .BR dirfd ():
  41 .br
  42 .RS 4
  43 .PD 0
  44 .ad l
  45 /* Since glibc 2.10: */ _POSIX_C_SOURCE\ >=\ 200809L
  46     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  47 .PD
  48 .RE
  49 .ad
  50 .SH DESCRIPTION
  51 The function
  52 .BR dirfd ()
  53 returns the file descriptor associated with the directory stream
  54 .IR dirp .
  55 .LP
  56 This file descriptor is the one used internally by the directory stream.
  57 As a result, it is useful only for functions which do not depend on
  58 or alter the file position, such as
  59 .BR fstat (2)
  60 and
  61 .BR fchdir (2).
  62 It will be automatically closed when
  63 .BR closedir (3)
  64 is called.
  65 .SH RETURN VALUE
  66 On success, a nonnegative file descriptor is returned.
  67 On error, \-1 is returned, and
  68 .I errno
  69 is set to indicate the cause of the error.
  70 .SH ERRORS
  71 POSIX.1-2008 specifies two errors,
  72 neither of which is returned by the current
  73 .\" glibc 2.8
  74 implementation.
  75 .TP
  76 .B EINVAL
  77 .I dirp
  78 does not refer to a valid directory stream.
  79 .TP
  80 .B ENOTSUP
  81 The implementation does not support the association of a file
  82 descriptor with a directory.
  83 .SH ATTRIBUTES
  84 For an explanation of the terms used in this section, see
  85 .BR attributes (7).
  86 .TS
  87 allbox;
  88 lb lb lb
  89 l l l.
  90 Interface       Attribute       Value
  91 T{
  92 .BR dirfd ()
  93 T}      Thread safety   MT-Safe
  94 .TE
  95 .SH CONFORMING TO
  96 POSIX.1-2008.
  97 This function was a BSD extension, present in 4.3BSD-Reno, not in 4.2BSD.
  98 .\" It is present in libc5 (since 5.1.2) and in glibc2.
  99 .SH SEE ALSO
 100 .BR open (2),
 101 .BR closedir (3),
 102 .BR opendir (3),
 103 .BR readdir (3),
 104 .BR rewinddir (3),
 105 .BR scandir (3),
 106 .BR seekdir (3),
 107 .BR telldir (3)