nag_file_open (x04ac) is especially useful if the calling language is not Fortran. It opens a Fortran unit number for reading, writing or appending, and associates the unit with a filename specified by the argument file.

References

None.

Parameters

Compulsory Input Parameters

1: $iounit$ – int64int32nag_int scalar

The Fortran unit number which identifies the file to be read from, written to or appended to. Note that this may be system dependent. Values in the range

7

1000

should however be safe on most systems.

2: $file$ – string

The name of the file to be opened.

Constraint: must contain a valid filename for the computer system being used.

3: $mode$ – int64int32nag_int scalar

Specifies whether the file is to be opened for reading, writing or appending.

$mode = 0$: The file is to be opened for reading.
$mode = 1$: The file is to be opened for writing.
$mode = 2$: The file is to be opened for appending.

Constraint:

0 \leq mode \leq 2

Optional Input Parameters

None.

Output Parameters

1: $ifail$ – int64int32nag_int scalar: $ifail = 0$ unless the function detects an error (see Error Indicators and Warnings).

Error Indicators and Warnings

Errors or warnings detected by the function:

$ifail = 1$: On entry, mode is invalid.

$ifail = 2$: Failure to open the file for reading.

$ifail = 3$: Failure to open the file for writing.

$ifail = 4$: Failure to open the file for appending.

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.

$ifail = - 999$: Dynamic memory allocation failed.

Accuracy

Not applicable.

Further Comments

None.

Example

This example illustrates how to open a file for writing.

Open in the MATLAB editor: x04ac_example

function x04ac_example


fprintf('x04ac example results\n\n');

file = 'success.res';

% Associate unit number iounit=4 with filename success.res
iounit = int64(4);

% Open File for writing to
mode = int64(1);
[ifail] = x04ac(iounit, file, mode);

% write to file here via iounit using x04ba
fprintf('The file named %s was opened for writing on unit number %d\n\n', ...
        file,iounit);
 
% Close File associated with unit number iounit=4
[ifail] = x04ad(iounit);
fprintf('Unit number %d has been closed\n', iounit);

delete(file);

x04ac example results

The file named success.res was opened for writing on unit number 4

Unit number 4 has been closed

PDF version (NAG web site, 64-bit version, 64-bit version)

Chapter Contents

Chapter Introduction

NAG Toolbox