ftell man page

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

Synopsis

#include <stdio.h>

long ftell(FILE *stream);
off_t ftello(FILE *stream);

Description

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 successful.

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.

Return Value

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.

Errors

The ftell() and ftello() functions shall fail if:

EBADF
The file descriptor underlying stream is not an open file descriptor.
EOVERFLOW
For ftell(), the current file offset cannot be represented correctly in an object of type long.
EOVERFLOW
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.

See Also

Section 2.5, Standard I/O Streams, fgetpos(), fopen(), fseek(), lseek()

The Base Definitions volume of POSIX.1‐2008, <stdio.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual