| MATLAB Functions | Help Desk |
fprintf
Write formatted data to file
count = fprintf(fid,format,A,...) fprintf(format,A,...)
count = fprintf(fid,format,A,...)
formats the data in the real part of matrix A (and in any additional matrix arguments) under control of the specified format string, and writes it to the file associated with file identifier fid. fprintf returns a count of the number of bytes written.
Argument fid is an integer file identifier obtained from fopen. (It may also be 1 for standard output (the screen) or 2 for standard error. See fopen for more information.) Omitting fid from fprintf's argument list causes output to appear on the screen, and is the same as writing to standard output (fid = 1)
fprintf(format,A,...)
writes to standard output--the screen.
The format string specifies notation, alignment, significant digits, field width, and other aspects of output format. It can contain ordinary alphanumeric characters; along with escape characters, conversion specifiers, and other characters, organized as shown below: 
For more information see "Tables" and "References".
The fprintf function behaves like its ANSI C language fprintf() namesake with certain exceptions and extensions. These include:
%o, %u, %x, and %X.The underlying C data type is a float rather than an unsigned integer. |
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The underlying C data type is a double rather than an unsigned integer. |
For example, to print a double-precision value in hexadecimal, use a format
like '%bx'.
fprintf function is vectorized for the case when input matrix A is nonscalar. The format string is cycled through the elements of A (columnwise) until all the elements are used up. It is then cycled in a similar manner, without reinitializing, through any additional matrix arguments.
Escape Characters
\'' or ''
Conversion Specifiers Exponential notation (using an uppercase The more compact of
E as in 3.1415E+00)
%e or %f, as defined in [2]. Insignificant zeros do not print.
% and the conversion character.
Other Characters A digit string specifying the minimum number of digits to be printed. A digit string including a period (.) specifying the number of digits to be printed to the right of the decimal point.
printf() and fprintf() routines in the documents listed in "References".
The statements
x = 0:.1:1;
y = [x; exp(x)];
fid = fopen('exp.txt','w');
fprintf(fid,'%6.2f %12.8f\n',y);
fclose(fid)
create a text file called exp.txt containing a short table of the exponential function:
0.00 1.00000000 0.10 1.10517092 ... 1.00 2.71828183The command
fprintf('A unit circle has circumference %g.\n',2*pi)
displays a line on the screen:
A unit circle has circumference 6.283186.To insert a single quotation mark in a string, use two single quotation marks together. For example,
displays on the screen:fprint(1,'It''sFriday.\n')
The commandsIt'sFriday.
B = [8.8 7.7; 8800 7700] fprintf(1,'X is %6.2f meters or %8.3f mm\n',9.9,9900,B)display the lines:
X is 9.90 meters or 9900.000 mm X is 8.80 meters or 8800.000 mm X is 7.70 meters or 7700.000 mmExplicitly convert MATLAB double-precision variables to integral values for use with an integral conversion specifier. For instance, to convert signed 32-bit data to hexadecimal format:
a = [6 10 14 44];
fprintf('%9X\n',a + (a<0)*2^32)
6
A
E
2C
fclose Close one or more open files
ferror Query MATLAB about errors in file input or output
fopen Open a file or obtain information about open files
fscanf Read formatted data from file
fseek Set file position indicator
ftell Get file position indicator