.\" -*- nroff -*-
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" $COPYRIGHT$
.TH MPI_Info_get_nthkey 3 "Sep 30, 2023" "4.1.6" "Open MPI"
.SH NAME
\fBMPI_Info_get_nthkey\fP \- Returns the \fIn\fPth defined key in \fIinfo\fP.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Info_get_nthkey(MPI_Info \fIinfo\fP, int \fIn\fP, char \fI*key\fP)

.fi
.SH Fortran Syntax
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INFO_GET_NTHKEY(\fIINFO, N, KEY, IERROR\fP)
	INTEGER		\fIINFO, N, IERROR\fP
	CHARACTER*(*)	\fIKEY\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Info_get_nthkey(\fIinfo\fP, \fIn\fP, \fIkey\fP, \fIierror\fP)
	TYPE(MPI_Info), INTENT(IN) :: \fIinfo\fP
	INTEGER, INTENT(IN) :: \fIn\fP
	CHARACTER(LEN=*), INTENT(OUT) :: \fIkey\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH C++ Syntax
.nf
#include <mpi.h>
void MPI::Info::Get_nthkey(int \fIn\fP, char* \fIkey\fP) const

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
info
Info object (handle).
.ft R
.TP 1i
n
Key number (integer).

.SH OUTPUT PARAMETERS
.ft R
.TP 1i
key
Key (string).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
MPI_Info_get_nthkey returns the \fIn\fPth defined key in \fIinfo\fP. Keys are numbered 0\...\fIN\fP - 1 where \fIN\fP is the value returned by MPI_Info_get_nkeys. All keys between 0 and \fIN\fP - 1 are guaranteed to be defined. The number of a given key does not change as long as \fIinfo\fP is not modified with MPI_Info_set or MPI_Info_delete.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

.SH SEE ALSO
.ft r
MPI_Info_get
.br
MPI_Info_get_nkeys
.br
MPI_Info_get_valuelen
.br