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.TH FTELL 3C "March 25, 2020"
.SH NAME
ftell, ftello \- return a file offset in a stream
.SH SYNOPSIS
.nf
#include <stdio.h>

\fBlong\fR \fBftell\fR(\fBFILE *\fR\fIstream\fR);
.fi

.LP
.nf
\fBoff_t\fR \fBftello\fR(\fBFILE *\fR\fIstream\fR);
.fi

.SH DESCRIPTION
The \fBftell()\fR function obtains the current value of the file-position
indicator for the stream pointed to by \fIstream\fR. The \fBftello()\fR
function is identical to \fBftell()\fR except for the return type.
.PP
Normally the value returned is measured in bytes. However, when
.I stream
has been created with
.B open_wmemstream(3C)
then the offset of the stream is measured in wide characters. This behavior is
consistent with how
.B fseek(3C)
and
.B fseeko(3C)
treat the offset into the stream.
.SH RETURN VALUES
Upon successful completion, the \fBftell()\fR and \fBftello()\fR 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
.B open_wmemstream(3C).
Otherwise, they return \fB\(mi1\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
The \fBftell()\fR and \fBftello()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The file descriptor underlying \fIstream\fR is not an open file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBESPIPE\fR\fR
.ad
.RS 10n
The file descriptor underlying \fIstream\fR is associated with a pipe, a FIFO,
or a socket.
.RE

.sp
.LP
The \fBftell()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
The current file offset cannot be represented correctly in an object of type
\fBlong\fR.
.RE

.sp
.LP
The \fBftello()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
The current file offset cannot be represented correctly in an object of type
\fBoff_t\fR.
.RE

.SH USAGE
The \fBftello()\fR function has a transitional interface for 64-bit file
offsets.  See \fBlf64\fR(7).
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.BR lseek (2),
.BR fopen (3C),
.BR fseek (3C),
.BR open_wmemstream (3C),
.BR attributes (7),
.BR lf64 (7),
.BR standards (7)