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.\" gd_getdata.3.  The gd_getdata man page.
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.\" under the terms of the GNU Free Documentation License, Version 1.2 or
.\" any later version published by the Free Software Foundation; with no
.\" Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
.\" Texts.  A copy of the license is included in the `COPYING.DOC' file
.\" as part of this distribution.
.\"
.TH gd_tell 3 "25 December 2016" "Version 0.10.0" "GETDATA"

.SH NAME
gd_tell \(em report the position of a Dirfile field I/O pointer

.SH SYNOPSIS
.SC
.B #include <getdata.h>
.HP
.BI "off_t gd_tell(DIRFILE *" dirfile ", const char *" field_code );
.EC

.SH DESCRIPTION
The
.FN gd_tell
function reports the current position of the I/O pointer of the field
.ARG field_code
in the dirfile(5) database specified by
.ARG dirfile .
.P
Only
.B RAW
fields (and the implicit
.I INDEX
field) have field pointers associated with them.  Calling
.FN gd_tell
on a derived field will report the position of the I/O pointer of the derived
field only if all of it's inputs are positioned the same.  Otherwise, an error
results.

.SH RETURN VALUE
Upon successful completion,
.FN gd_tell
returns a non-negative integer indicating the I/O position of the specified
field in samples.  On error, it returns a negative-valued error code.  Possible
error codes are:
.DD GD_E_ALLOC
The library was unable to allocate memory.
.DD GD_E_BAD_CODE
The field specified by
.ARG field_code ,
or one of the fields it uses for input, was not found in the database.
.DD GD_E_BAD_DIRFILE
The supplied dirfile was invalid.
.DD GD_E_DIMENSION
The specified field or one of its inputs wasn't of vector type.
.DD GD_E_DOMAIN
The I/O position of a derived field wasn't well defined because its input fields
simultaneously read from different places in the same
.B RAW
field.
.DD GD_E_INTERNAL_ERROR
An internal error occurred in the library while trying to perform the task.
This indicates a bug in the library.  Please report the incident to the
maintainer.
.DD GD_E_IO
An error occurred while trying to open or read from a file on disk containing
a raw field.
.DD GD_E_RECURSE_LEVEL
Too many levels of recursion were encountered while trying to resolve
.ARG field_code .
This usually indicates a circular dependency in field specification in the
dirfile.
.DD GD_E_UNKNOWN_ENCODING
The encoding scheme of a RAW field could not be determined.  This may also
indicate that the binary file associated with the RAW field could not be found.
.DD GD_E_UNSUPPORTED
Reading from dirfiles with the encoding scheme of the specified dirfile is not
supported by the library.  See
dirfile-encoding(5)
for details on dirfile encoding schemes.
.PP
The error code is also stored in the
.B DIRFILE
object and may be retrieved after this function returns by calling
.F3 gd_error .
A descriptive error string for the error may be obtained by calling
.F3 gd_error_string .

.SH HISTORY
The
.FN gd_tell
function appeared in GetData-0.8.0.

In GetData-0.10.0, the error return from this function changed from -1 to a
negative-valued error code.

.SH SEE ALSO
.F3 gd_getdata ,
.F3 gd_open ,
.F3 gd_putdata ,
.F3 gd_seek .