`fwrite`

Writes binary data to a file.

Category: Data Import and Analysis > Data Import and Export

Syntax

count = fwrite(fid, A)

Writes the elements of A as unsigned bytes.

count = fwrite(fid, A, precision)

Writes in the given type, such as 'int16' or 'double'.

count = fwrite(fid, A, precision, skip, machinefmt)

Skips bytes between values and sets the byte order.

Description

Values are converted to the requested type before writing, saturating at its limits. The result is a raw byte stream with no header, so whoever reads it must know the type and byte order. Pair it with fread using the same precision.

Input arguments

A: Numeric or character data, written in column order.
precision: Output type: 'uint8' (default), 'int8', 'uint16', 'int16', 'uint32', 'int32', 'single', 'double', 'char'.
machinefmt: 'l' for little-endian or 'b' for big-endian.

Output arguments

count: Number of elements written.

Example

Bytes and 16-bit values

fid = fopen('b.bin', 'w');
n1 = fwrite(fid, [1 2 3])
n2 = fwrite(fid, [1 300], 'uint16')
fclose(fid);
d = dir('b.bin'); d.bytes
fid = fopen('b.bin');
fread(fid, 3)'
fread(fid, 2, 'uint16')'
fclose(fid);

Output

n1 = 3
n2 = 2
ans = 7
ans = 1×3

     1     2     3
ans = 1×2

     1   300

fwrite