Matlab fwrite

Introduction to Matlab fwrite

In some applications, there is a need to access the text file to do operations like data reading from a text file, data writing on a text file. To write data to the binary file we use a fwrite statement. fwrite is an inbuilt function available on Matlab for writing data on a binary file ( .bin extension). For writing a data firstly we must need to open that file using a fopen statement and we specify the type of access mode to write ‘w’.

Syntax

The syntax for fwrite Matlab is as shown below:

fwrite(fileID1,A)
fwrite(fileID1,A,precision)
fwrite(fileID1,A,precision,skip)
fwrite(fileID1,A,precision,skip,machinefmt)
count = fwrite(___)

How to do Matlab fwrite?

For writing a data on text file we use a fwrite statement. For writing data to the binary file, we need to open that binary file using a fopen statement. In the fopen statement, we write a binary file name that we want to open and specify a type of access mode.

The steps for writing a data on text file using a fwrite statement:

Step 1: First open a file using fopen statement and specify the type of access mode to ‘w’.

Step 2: Then we use a fwrite statement for writing a data to a binary file

Step 3: Close the file using fclose statement.

Step 4: For verification, we use a type function, type function displays the contents of the file.

Examples to Implement Matlab fwrite

Below are the examples mentioned :

Example #1

Let us see an example for a fwrite statement, basically, a fwrite statement is used to write data on binary files.

For writing a data on binary file we need to create a binary file, the binary file is a nothing but a file with extension .bin. We create a binary file with a name ten.bin. For writing data on that ten.bin file we need to open that file using a fopen statement and also we specify the type of access mode that is writing. We take a fopen statement in parenthesis we write a binary file name ten.bin and we specify the type of access mode to write ‘w’. Fopen statement returns a data to fileID1, fileID1 is a file identifier of an open binary file. Then we use a fwrite statement to write a data on a binary file, the data is nothing but a 1 to 10 numbers write on that binary file. And then we close a file using a fclose statement.

Code:

clc;
clear all;
close all;
fileID1 = fopen('ten.bin','w');
fwrite(fileID1, [1:10]);fclose(fileID1);

Output:

Example #2

Let see another example for a fwrite statement, for writing a data on binary file we need to create a binary file, the binary file is a nothing but a file with extension .bin. We create a binary file with a name mydoc1.bin. For writing data on that mydoc1.bin file we need to open that file using a fopen statement and also we specify the type of access mode that is writing.

We take a fopen statement in parenthesis we write a binary file name mydoc1.bin and we specify the type of access mode to write ‘w’. Fopen statement returns a data to fileID1, fileID1 is a file identifier of an open binary file.

Then we use a fwrite statement to write a data on a binary file, w first take a file identifier as an argument fileID1, then take magic(3) it generates a 3-by-3 magic square, and we take precision as a double. The data is nothing but a 3-by-3 magic square writes on that binary file. And then we close a file using a fclose statement.

Code:

clc;
clear all;
close all;
fileID1 = fopen('mydoc1.bin','w');
fwrite(fileID1,magic(3),'double');
fclose(fileID1);

Output:

Explanation: As we saw both the example we cannot saw results on a command window but the data is written to a binary file.

Example #3

Let us see an example, by using fwrite statement we can write data to a binary file, but that data we cannot see on command window or if we open that file also we can’t read that file because it’s data written in binary format so we need to open that file using a fread statement, fread statement used to read data from a binary file. In this example, we write data on a binary file that data is a 3-by-3 magic square using a fwrite statement. We open a file using a fopen statement and then write a data to a binary file using a fwrite statement and then we close that file using a fclose statement. Then to verify that the written data to a binary file is correct or not we must need to read data from the binary file we use fread statement and verified the data. For that, we open that binary file using a fopen statement and then use a fread statement for reading data from a binary file and display the data on the command window and then close the file using a fopen statement.

Code:

clc;
clear all;
close all;
fileID1 = fopen('mydoc1.bin','w');
fwrite(fileID1,magic(3),'double');
fclose(fileID1);
fileID1 = fopen('mydoc1.bin');
R1 = fread(fileID1,[3 3],'double')
fclose(fileID1);

Output:

Conclusion

In this article we saw the concept of fwrite; basically fwrite is used for writing data to a binary file. Then saw syntax related to fwrite statements and how it’s used in Matlab code for writing a data to a binary file. Also, we saw some examples related to the fwrite statement.

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