NAME

ftell, ftello - return a file offset in a stream

SYNOPSIS

#include <stdio.h>

long ftell(FILE *stream);


[CX] off_t ftello(FILE *stream);

DESCRIPTION

^[CX] 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.

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

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

RETURN VALUE

Upon successful completion, ftell() ^[CX]  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() ^[CX]  and ftello() shall return -1, cast to long and off_t respectively, and set errno to indicate the error.

ERRORS

The ftell() ^[CX]  and ftello() functions shall fail if:

[EBADF]

^[CX] The file descriptor underlying stream is not an open file descriptor.

[EOVERFLOW]

^[CX] For ftell(), the current file offset cannot be represented correctly in an object of type long.

[EOVERFLOW]

^[CX] For ftello(), the current file offset cannot be represented correctly in an object of type off_t.

[ESPIPE]

^[CX] The file descriptor underlying stream is associated with a pipe or FIFO.

The ftell() function may fail if:

[ESPIPE]

^[CX] The file descriptor underlying stream is associated with a socket.

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:

• The ftello() function is added.

• The [EOVERFLOW] error conditions are added.

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