.\" gd_aliases.3.  The gd_aliases man page.
.\"
.\" Copyright (C) 2012 D. V. Wiebe
.\"
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.TH gd_aliases 3 "1 January 2012" "Version 0.8.0" "GETDATA"
.SH NAME
gd_aliases \(em retrieve a list of aliases for a field in a dirfile database
.SH SYNOPSIS
.B #include <getdata.h>
.HP
.nh
.ad l
.BI "const char **gd_aliases(DIRFILE *" dirfile ", const char *" field_code );
.hy
.ad n
.SH DESCRIPTION
The
.BR gd_aliases ()
function queries a dirfile(5) database specified by
.I dirfile
and returns a read-only list of aliases of the field specified by
.IR field_code .

The
.I dirfile
argument must point to a valid DIRFILE object previously created by a call to
.BR gd_open (3).

The array returned will be de-allocated by a call to
.BR gd_close (3)
and should not be de-allocated by the caller.  The list returned should not be
assumed to be in any particular order.  The array is terminated by a NULL
pointer.  The number of strings in the array can be obtained from a call to
.BR gd_naliases (3).

The caller may not modify any strings in the array, or the array itself.  Doing
so may cause database corruption.  The pointer returned is guaranteed to be
valid until
.BR gd_aliases ()
is called again with the same arguments, or until the array is de-allocated by
a call to
.BR gd_close (3).

.SH RETURN VALUE
Upon successful completion,
.BR gd_aliases ()
returns a pointer to an array of strings containing the values of all the
aliases for the specified field.  The array is terminated by a NULL pointer.
If successful, this list will always contain at least one entry, to wit:
.IR field_code .

On error it returns NULL and sets the dirfile error to a non-zero error value.
Possible error values are:
.TP 8
.B GD_E_ALLOC
The library was unable to allocate memory.
.TP
.B GD_E_BAD_CODE
The specified field code was not found in the database.
.TP
.B GD_E_BAD_DIRFILE
The supplied dirfile was invalid.
.PP
The dirfile error may be retrieved by calling
.BR gd_error (3).
A descriptive error string for the last error encountered can be obtained from
a call to
.BR gd_error_string (3).
.SH SEE ALSO
.BR dirfile (5),
.BR gd_open (3),
.BR gd_alias_target (3),
.BR gd_naliases (3)