.\" Copyright 2001 Andries Brouwer . .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .TH FSEEKO 3 2017-09-15 "" "Linux Programmer's Manual" .SH NAME fseeko, ftello \- seek to or report file position .SH SYNOPSIS .nf .B #include .PP .BI "int fseeko(FILE *" stream ", off_t " offset ", int " whence ); .PP .BI "off_t ftello(FILE *" stream ); .BI .fi .PP .in -4n Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .in .PP .BR fseeko (), .BR ftello (): .br .RS 4 .ad l _FILE_OFFSET_BITS\ ==\ 64 || _POSIX_C_SOURCE\ >=\ 200112L .br (defining the obsolete _LARGEFILE_SOURCE macro also works) .RE .ad .SH DESCRIPTION The .BR fseeko () and .BR ftello () functions are identical to .BR fseek (3) and .BR ftell (3) (see .BR fseek (3)), respectively, except that the .I offset argument of .BR fseeko () and the return value of .BR ftello () is of type .I off_t instead of .IR long . .PP On some architectures, both .IR off_t and .I long are 32-bit types, but defining .BR _FILE_OFFSET_BITS with the value 64 (before including .I any header files) will turn .I off_t into a 64-bit type. .SH RETURN VALUE On successful completion, .BR fseeko () returns 0, while .BR ftello () returns the current offset. Otherwise, \-1 is returned and .I errno is set to indicate the error. .SH ERRORS See the ERRORS in .BR fseek (3). .SH VERSIONS These functions are available under glibc since version 2.1. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbw18 lb lb l l l. Interface Attribute Value T{ .BR fseeko (), .BR ftello () T} Thread safety MT-Safe .TE .sp 1 .SH CONFORMING TO POSIX.1-2001, POSIX.1-2008, SUSv2. .SH SEE ALSO .BR fseek (3) .SH COLOPHON This page is part of release 4.16 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.