.\" -*- nroff -*- .\" Copyright 2010 Cisco Systems, Inc. All rights reserved. .\" Copyright 2006-2008 Sun Microsystems, Inc. .\" Copyright (c) 1996 Thinking Machines Corporation .\" Copyright 2015-2016 Research Organization for Information Science .\" and Technology (RIST). All rights reserved. .\" $COPYRIGHT$ .TH MPI_File_read 3 "May 26, 2022" "4.1.4" "Open MPI" .SH NAME \fBMPI_File_read\fP \- Reads a file starting at the location specified by the individual file pointer (blocking, noncollective). .SH SYNTAX .ft R .nf .SH C Syntax .nf #include int MPI_File_read(MPI_File \fIfh\fP, void \fI*buf\fP, int \fIcount\fP, MPI_Datatype \fIdatatype\fP, MPI_Status \fI*status\fP) .fi .SH Fortran Syntax .nf USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_FILE_READ(\fIFH\fP, \fIBUF\fP, \fICOUNT\fP, \fIDATATYPE\fP, \fISTATUS\fP, \fIIERROR\fP) \fIBUF(*)\fP INTEGER \fIFH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE),IERROR\fP .fi .SH Fortran 2008 Syntax .nf USE mpi_f08 MPI_File_read(\fIfh\fP, \fIbuf\fP, \fIcount\fP, \fIdatatype\fP, \fIstatus\fP, \fIierror\fP) TYPE(MPI_File), INTENT(IN) :: \fIfh\fP TYPE(*), DIMENSION(..) :: \fIbuf\fP INTEGER, INTENT(IN) :: \fIcount\fP TYPE(MPI_Datatype), INTENT(IN) :: \fIdatatype\fP TYPE(MPI_Status) :: \fIstatus\fP INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP .fi .SH C++ Syntax .nf #include void MPI::File::Read(void* \fIbuf\fP, int \fIcount\fP, const MPI::Datatype& \fIdatatype\fP, MPI::Status& \fIstatus\fP) void MPI::File::Read(void* \fIbuf\fP, int \fIcount\fP, const MPI::Datatype& \fIdatatype\fP) .fi .SH INPUT PARAMETERS .ft R .TP 1i fh File handle (handle). .TP 1i count Number of elements in buffer (integer). .TP 1i datatype Data type of each buffer element (handle). .SH OUTPUT PARAMETERS .ft R .TP 1i buf Initial address of buffer (integer). .TP 1i status Status object (status). .TP 1i IERROR Fortran only: Error status (integer). .SH DESCRIPTION .ft R MPI_File_read attempts to read from the file associated with .I fh (at the current individual file pointer position maintained by the system) a total number of .I count data items having .I datatype type into the user's buffer .I buf. The data is taken out of those parts of the file specified by the current view. MPI_File_read stores the number of data-type elements actually read in .I status. All other fields of .I status are undefined. .sp It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened. .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. For MPI I/O function errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler may be changed with MPI_File_set_errhandler; the predefined error handler MPI_ERRORS_ARE_FATAL may be used to make I/O errors fatal. Note that MPI does not guarantee that an MPI program can continue past an error.