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 .fi
  36 .PP
  37 .in -4n
  38 Feature Test Macro Requirements for glibc (see
  39 .BR feature_test_macros (7)):
  40 .in
  41 .PP
  42 .BR fseeko (),
  43 .BR ftello ():
  44 .br
  45 .RS 4
  46 .ad l
  47 _FILE_OFFSET_BITS\ ==\ 64 || _POSIX_C_SOURCE\ >=\ 200112L
  48 .br
  49 (defining the obsolete _LARGEFILE_SOURCE macro also works)
  50 .RE
  51 .ad
  52 .SH DESCRIPTION
  53 The
  54 .BR fseeko ()
  55 and
  56 .BR ftello ()
  57 functions are identical to
  58 .BR fseek (3)
  59 and
  60 .BR ftell (3)
  61 (see
  62 .BR fseek (3)),
  63 respectively, except that the
  64 .I offset
  65 argument of
  66 .BR fseeko ()
  67 and the return value of
  68 .BR ftello ()
  69 is of type
  70 .I off_t
  71 instead of
  72 .IR long .
  73 .PP
  74 On some architectures, both
  75 .IR off_t
  76 and
  77 .I long
  78 are 32-bit types, but defining
  79 .BR _FILE_OFFSET_BITS
  80 with the value 64 (before including
  81 .I any
  82 header files)
  83 will turn
  84 .I off_t
  85 into a 64-bit type.
  86 .SH RETURN VALUE
  87 On successful completion,
  88 .BR fseeko ()
  89 returns 0, while
  90 .BR ftello ()
  91 returns the current offset.
  92 Otherwise, \-1 is returned and
  93 .I errno
  94 is set to indicate the error.
  95 .SH ERRORS
  96 See the ERRORS in
  97 .BR fseek (3).
  98 .SH VERSIONS
  99 These functions are available under glibc since version 2.1.
 100 .SH ATTRIBUTES
 101 For an explanation of the terms used in this section, see
 102 .BR attributes (7).
 103 .TS
 104 allbox;
 105 lbw18 lb lb
 106 l l l.
 107 Interface       Attribute       Value
 108 T{
 109 .BR fseeko (),
 110 .BR ftello ()
 111 T}      Thread safety   MT-Safe
 112 .TE
 113 .sp 1
 114 .SH CONFORMING TO
 115 POSIX.1-2001, POSIX.1-2008, SUSv2.
 116 .SH SEE ALSO
 117 .BR fseek (3)