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.\" gd_validate.3.  The gd_validate man page.
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.\" This file is part of the GetData project.
.\"
.\" Permission is granted to copy, distribute and/or modify this document
.\" 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_validate 3 "25 December 2016" "Version 0.10.0" "GETDATA"

.SH NAME
gd_validate \(em check a Dirfile field code for validity

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

.SH DESCRIPTION
The
.FN gd_validate
function queries a dirfile(5) database specified by
.ARG dirfile
and checks whether
.ARG field_code ,
which may contain a representation suffix, specifies a valid field.

The 
.ARG dirfile
argument must point to a valid DIRFILE object previously created by a call to
.F3 gd_open .

This function checks whether the field and its input fields (if any) are found,
and also that all non-literal parameters specify valid scalar fields.

.SH RETURN VALUE
If all checks pass,
.FN gd_validate
returns zero.  On error, it returns a negative-valued error code.  Possible
error codes are:
.DD GD_E_BAD_CODE
The field specified by
.ARG field_code
or one of the fields it uses as input was not found in the database.
.DD GD_E_BAD_DIRFILE
The supplied dirfile was invalid.
.DD GD_E_BAD_SCALAR
A non-literal scalar used in the definition of the field or one of its inputs
was not found, or was not a
.B CONST
or
.B CARRAY
field.
.DD GD_E_DIMENSION
A scalar field was found where a vector field was expected.
.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 NOTES
It is not necessary to call this function before passing a field code to another
GetData function: all functions which accept field codes perform these checks
themselves.

.SH HISTORY
The
.F3 dirfile_validate
function appared in GetData-0.6.0.

In GetData-0.7.0, this function was renamed to
.F3 gd_validate .

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_error ,
.F3 gd_error_string ,
.F3 gd_getdata ,
.F3 gd_open ,
dirfile(5)