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.
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-
position indicator for the stream pointed to by stream.
The ftell() function shall not change the setting of errno if
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
current 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
indicate 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
correctly in an object of type long.
For ftello(), the current file offset cannot be represented
correctly 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.
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 Electrical 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
IEEE/The Open Group 2013 FTELL(3P)