man3/fseeko.3

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  25 .TH FSEEKO 3  2017-09-15 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 fseeko, ftello \- seek to or report file position
  28 .SH SYNOPSIS
  29 .nf
  30 .B #include <stdio.h>
  31 .PP
  32 .BI "int fseeko(FILE *" stream ", off_t " offset ", int " whence );
  33 .PP
  34 .BI "off_t ftello(FILE *" stream );
  35 .BI
  36 .fi
  37 .PP
  38 .in -4n
  39 Feature Test Macro Requirements for glibc (see
  40 .BR feature_test_macros (7)):
  41 .in
  42 .PP
  43 .BR fseeko (),
  44 .BR ftello ():
  45 .br
  46 .RS 4
  47 .ad l
  48 _FILE_OFFSET_BITS\ ==\ 64 || _POSIX_C_SOURCE\ >=\ 200112L
  49 .br
  50 (defining the obsolete _LARGEFILE_SOURCE macro also works)
  51 .RE
  52 .ad
  53 .SH DESCRIPTION
  54 The
  55 .BR fseeko ()
  56 and
  57 .BR ftello ()
  58 functions are identical to
  59 .BR fseek (3)
  60 and
  61 .BR ftell (3)
  62 (see
  63 .BR fseek (3)),
  64 respectively, except that the
  65 .I offset
  66 argument of
  67 .BR fseeko ()
  68 and the return value of
  69 .BR ftello ()
  70 is of type
  71 .I off_t
  72 instead of
  73 .IR long .
  74 .PP
  75 On some architectures, both
  76 .IR off_t
  77 and
  78 .I long
  79 are 32-bit types, but defining
  80 .BR _FILE_OFFSET_BITS
  81 with the value 64 (before including
  82 .I any
  83 header files)
  84 will turn
  85 .I off_t
  86 into a 64-bit type.
  87 .SH RETURN VALUE
  88 On successful completion,
  89 .BR fseeko ()
  90 returns 0, while
  91 .BR ftello ()
  92 returns the current offset.
  93 Otherwise, \-1 is returned and
  94 .I errno
  95 is set to indicate the error.
  96 .SH ERRORS
  97 See the ERRORS in
  98 .BR fseek (3).
  99 .SH VERSIONS
 100 These functions are available under glibc since version 2.1.
 101 .SH ATTRIBUTES
 102 For an explanation of the terms used in this section, see
 103 .BR attributes (7).
 104 .TS
 105 allbox;
 106 lbw18 lb lb
 107 l l l.
 108 Interface       Attribute       Value
 109 T{
 110 .BR fseeko (),
 111 .BR ftello ()
 112 T}      Thread safety   MT-Safe
 113 .TE
 114 .sp 1
 115 .SH CONFORMING TO
 116 POSIX.1-2001, POSIX.1-2008, SUSv2.
 117 .SH SEE ALSO
 118 .BR fseek (3)