FTELL(3P) POSIX Programmer's Manual FTELL(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
ftell, ftello — return a file offset in a stream
long ftell(FILE *stream);
off_t ftello(FILE *stream);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here
and the ISO C standard is unintentional. This volume of POSIX.1‐2008
defers to the ISO C standard.
The ftell() function shall obtain the current value of the file-posi‐
tion indicator for the stream pointed to by stream.
The ftell() function shall not change the setting of errno if success‐
The ftello() function shall be equivalent to ftell(), except that the
return value is of type off_t and the ftello() function may change the
setting of errno if successful.
Upon successful completion, ftell() and ftello() shall return the cur‐
rent value of the file-position indicator for the stream measured in
bytes from the beginning of the file.
Otherwise, ftell() and ftello() shall return −1, and set errno to indi‐
cate the error.
The ftell() and ftello() functions shall fail if:
EBADF The file descriptor underlying stream is not an open file
For ftell(), the current file offset cannot be represented cor‐
rectly in an object of type long.
For ftello(), the current file offset cannot be represented cor‐
rectly in an object of type off_t.
ESPIPE The file descriptor underlying stream is associated with a pipe,
FIFO, or socket.
The following sections are informative.
Section 2.5, Standard I/O Streams, fgetpos(), fopen(), fseek(), lseek()
The Base Definitions volume of POSIX.1‐2008, <stdio.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
IEEE/The Open Group 2013 FTELL(3P)