MPI\_INFO\_GET(3) Open MPI MPI\_INFO\_GET(3)

MPI\_Info\_get — Retrieves the value associated with a key in an info object.

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Info_get(MPI_Info info, const char *key, int valuelen, char *value, int *flag)
```

## [Fortran Syntax](#Fortran_Syntax)

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INFO_GET(INFO, KEY, VALUELEN, VALUE, FLAG, IERROR)


     INTEGER INFO, VALUELEN, IERROR


     CHARACTER*(*) KEY, VALUE


     LOGICAL FLAG
```

## [Fortran 2008 Syntax](#Fortran_2008_Syntax)

```
USE mpi_f08
MPI_Info_get(info, key, valuelen, value, flag, ierror)


     TYPE(MPI_Info), INTENT(IN) :: info


     CHARACTER(LEN=*), INTENT(IN) :: key


     INTEGER, INTENT(IN) :: valuelen


     CHARACTER(LEN=valuelen), INTENT(OUT) :: value


     LOGICAL, INTENT(OUT) :: flag


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

# [INPUT PARAMETERS](#INPUT_PARAMETERS)

- **info**: Info object (handle).
- **key**: Key (string).
- **valuelen**: Length of value arg (integer).

# [OUTPUT PARAMETER](#OUTPUT_PARAMETER)

- **value**: Value (string).
- **flag**: Returns true if key defined, false if not (boolean).
- **ierror**: Fortran only: Error status (integer).

# [DESCRIPTION](#DESCRIPTION)

MPI\_Info\_get retrieves the value associated with *key* in a previous call to MPI\_Info\_set &lt;#mpi-info-set&gt;. If such a key exists, it sets *flag* to true and returns the value in *value*; otherwise it sets *flag* to false and leaves *value* unchanged. *valuelen* is the number of characters available in value. If it is less than the actual size of the value, the returned value is truncated. In C, *valuelen* should be one less than the amount of allocated space to allow for the null terminator.

If *key* is larger than MPI\_MAX\_INFO\_KEY, the call is erroneous.

# [ERRORS](#ERRORS)

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI\_COMM\_SELF and will call the associated MPI error handler. When MPI\_COMM\_SELF is not initialized (i.e., before MPI\_Init &lt;#mpi-init&gt;/MPI\_Init\_thread &lt;#mpi-init-thread&gt;, after MPI\_Finalize &lt;#mpi-finalize&gt;, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI\_Comm\_set\_errhandler &lt;#mpi-comm-set-errhandler&gt; on MPI\_COMM\_SELF when using the World model, or the mpi\_initial\_errhandler CLI argument to mpiexec or info key to MPI\_Comm\_spawn &lt;#mpi-comm-spawn&gt;/MPI\_Comm\_spawn\_multiple &lt;#mpi-comm-spawn-multiple&gt;. If no other appropriate error handler has been set, then the MPI\_ERRORS\_RETURN error handler is called for MPI I/O functions and the MPI\_ERRORS\_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

- **MPI\_ERRORS\_ARE\_FATAL** Causes the program to abort all connected MPI processes.
- **MPI\_ERRORS\_ABORT** An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI\_Abort &lt;#mpi-abort&gt; was called on that communicator. If called on a window or file, acts as if MPI\_Abort &lt;#mpi-abort&gt; was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
- **MPI\_ERRORS\_RETURN** Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

- MPI\_Comm\_create\_errhandler &lt;#mpi-comm-create-errhandler&gt; then MPI\_Comm\_set\_errhandler &lt;#mpi-comm-set-errhandler&gt;
- MPI\_File\_create\_errhandler &lt;#mpi-file-create-errhandler&gt; then MPI\_File\_set\_errhandler &lt;#mpi-file-set-errhandler&gt;
- MPI\_Session\_create\_errhandler &lt;#mpi-session-create-errhandler&gt; then MPI\_Session\_set\_errhandler &lt;#mpi-session-set-errhandler&gt; or at MPI\_Session\_init &lt;#mpi-session-init&gt;
- MPI\_Win\_create\_errhandler &lt;#mpi-win-create-errhandler&gt; then MPI\_Win\_set\_errhandler &lt;#mpi-win-set-errhandler&gt;

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page &lt;#open-mpi&gt; for a full list of MPI error codes &lt;#open-mpi-errors&gt;.

See the Error Handling section of the MPI-3.1 standard for more information.

**See also:**

- MPI\_Info\_create &lt;#mpi-info-create&gt;
- MPI\_Info\_delete &lt;#mpi-info-delete&gt;
- MPI\_Info\_dup &lt;#mpi-info-dup&gt;
- MPI\_Info\_free &lt;#mpi-info-free&gt;
- MPI\_Info\_get\_valuelen &lt;#mpi-info-get-valuelen&gt;
- MPI\_Info\_get\_nkeys &lt;#mpi-info-get-nkeys&gt;
- MPI\_Info\_get\_nthkey &lt;#mpi-info-get-nthkey&gt;
- MPI\_Info\_set &lt;#mpi-info-set&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

July 6, 2026

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Document: MPI_Info_get(3) from openmpi-cuda-12.4 5.0.10-r2 (Chainguard OS)
Source: https://github.com/open-mpi/ompi