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FTELL 3C "March 25, 2020"
NAME
ftell, ftello - return a file offset in a stream
SYNOPSIS
#include <stdio.h> long ftell(FILE *stream);
off_t ftello(FILE *stream);
DESCRIPTION
The ftell() function obtains the current value of the file-position
indicator for the stream pointed to by stream. The ftello()
function is identical to ftell() except for the return type.
Normally the value returned is measured in bytes. However, when stream has been created with open_wmemstream(3C) then the offset of the stream is measured in wide characters. This behavior is consistent with how fseek(3C) and fseeko(3C) treat the offset into the stream.
RETURN VALUES
Upon successful completion, the ftell() and ftello() functions
return the current value of the file-position indicator for the stream measured
in bytes from the beginning of the file, or wide characters for streams created
by
open_wmemstream(3C). Otherwise, they return -1 and sets errno to indicate the error.
ERRORS
The ftell() and ftello() functions will fail if:
EBADF
The file descriptor underlying stream is not an open file descriptor.
The file descriptor underlying stream is associated with a pipe, a FIFO, or a socket.
The ftell() function will fail if: EOVERFLOW
The current file offset cannot be represented correctly in an object of type long.
The ftello() function will fail if: EOVERFLOW
The current file offset cannot be represented correctly in an object of type off_t.
USAGE
The ftello() function has a transitional interface for 64-bit file
offsets. See lf64(7).
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface Stability Standard |
| MT-Level MT-Safe |
SEE ALSO
lseek (2), fopen (3C), fseek (3C), open_wmemstream (3C), attributes (7), lf64 (7), standards (7)