fprintf

Writes data to a file.

📝Syntax

fprintf(format, v1, ... , vn)
fprintf(fid, format, v1, ... , vn)
R = fprintf(fid, format, v1, ... , vn)

📥Input Arguments

Parameter	Description
fid	a file descriptor
format	a string describing the format to used_function.
v1, ... , vn	data to convert and print according to the previous format parameter.

📤Output Arguments

Parameter	Description
R	an integer value: number of bytes written to a file, or number of visible characters displayed on screen.

📄Description

Write data in text form to the file specified by the file descriptor fid.

characters encoding uses fopen parameter.

If fid equals 1 redirection in stdout.

If fid equals 2 redirection in stderr.

When output is sent to the screen, ANSI SGR escape sequences can style text with bold, italic, underline, strikethrough, foreground colors, and background colors. The escape sequences are interpreted for stdout and stderr display, but they are written unchanged when output is sent to a file.

The format follows C fprintf syntax.

Value type	format	comment
Integer	%i	base 10
Integer signed	%d	base 10
Integer unsigned	%u	base 10
Integer	%o	Octal (base 8)
Integer	%x	Hexadecimal (lowercase)
Integer	%X	Hexadecimal (uppercase)
Floating-point number	%f	Fixed-point notation
Floating-point number	%e	Exponential notation (lowercase)
Floating-point number	%E	Exponential notation (uppercase)
Floating-point number	%g	Exponential notation (compact format, lowercase)
Floating-point number	%G	Exponential notation (compact format, uppercase)
Character	%c	Single character
String	%s	Character vector.

To display a percent sign, you need to use a double percent sign (%%) in the format string.

A percent sign at the end of the format string that is not doubled is ignored.

💡Examples

fileID = fopen([tempdir(), 'fprintf.txt'],'wt');
fprintf(fileID, 'an example of %s.', 'text');
fclose(fileID);

R = fileread([tempdir(), 'fprintf.txt'])

fprintf(1, 'an value %g.', pi);
fprintf(2, "an value %g.", pi);

Display styled text with ANSI SGR escape sequences

esc = char(27);
fprintf([esc, '[1;34mBold blue text', esc, '[0m\n']);

Display truecolor text with ANSI SGR escape sequences

esc = char(27);
fprintf([esc, '[38;2;80;120;220mTruecolor text', esc, '[0m\n']);

How to use backspace

reverseStr = '';
for idx = 1 : 100
 percentDone = idx;
 msg = sprintf('Percent done: %3.1f', percentDone);
 fprintf([reverseStr, msg]);
 reverseStr = repmat(sprintf('\b'), 1, length(msg));
end

Display a percent sign

fprintf(1, '%d%%.', 95)

Trailing percent handling

fprintf(1, ' %d %', 10)
fprintf(1, ' %d %%', 10)

🔗See Also

fopen fclose fread

🕔Version History

Version	Description
1.0.0	initial version
2.0.0	ANSI SGR escape sequences are rendered for screen output.

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