The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
A newer edition of this document exists here

NAME

ftell, ftello - return a file offset in a stream

SYNOPSIS

#include <stdio.h>

long ftell(FILE *
stream);

[CX] [Option Start] off_t ftello(FILE *stream); [Option End]

DESCRIPTION

[CX] [Option Start] 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 IEEE Std 1003.1-2001 defers to the ISO C standard. [Option End]

The ftell() function shall obtain the current value of the file-position indicator for the stream pointed to by stream.

[CX] [Option Start] The ftello() function shall be equivalent to ftell(), except that the return value is of type off_t. [Option End]

RETURN VALUE

Upon successful completion, ftell() [CX] [Option Start]  and ftello() [Option End]  shall return the current value of the file-position indicator for the stream measured in bytes from the beginning of the file.

Otherwise, ftell() [CX] [Option Start]  and ftello() [Option End] shall return -1, cast to long and off_t respectively, and set errno to indicate the error.

ERRORS

The ftell() [CX] [Option Start]  and ftello() [Option End] functions shall fail if:

[EBADF]
[CX] [Option Start] The file descriptor underlying stream is not an open file descriptor. [Option End]
[EOVERFLOW]
[CX] [Option Start] For ftell(), the current file offset cannot be represented correctly in an object of type long. [Option End]
[EOVERFLOW]
[CX] [Option Start] For ftello(), the current file offset cannot be represented correctly in an object of type off_t. [Option End]
[ESPIPE]
[CX] [Option Start] The file descriptor underlying stream is associated with a pipe or FIFO. [Option End]

The ftell() function may fail if:

[ESPIPE]
[CX] [Option Start] The file descriptor underlying stream is associated with a socket. [Option End]

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

fgetpos(), fopen(), fseek() , lseek(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 5

Large File Summit extensions are added.

Issue 6

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

An additional [ESPIPE] error condition is added for sockets.

End of informative text.

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POSIX ® is a registered Trademark of The IEEE.
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