Write formatted data to file.
count = fprintf(fid,'format',A,...)
fprintf('format',A,...)
count = fprintf(fid,'format',A,...) formats the data in 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. count is the integer number of bytes written.
fid is an integer file identifier obtained from fopen. It can also be 1 for standard output (the screen) or 2 for standard error. On some computers, fopen can be used with device names. For example, in an MS-DOS environment, COM1 might be defined as a serial port leading to a modem. In that case, use fopen('COM1') and fprintf to send characters to the modem.
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).
format is a string containing ordinary characters and/or conversion specifications. Ordinary characters include the normal alphanumeric characters, and escape characters. Escape characters include
------------------
\n new line
\t horizontal tab
\b backspace
\r carriage return
\f form feed
\ backslash
------------------
Conversion specifications involve the character %, optional width fields, and conversion characters. Legal conversion characters are
-------------------------------------------------------------
%e exponential notation
%f fixed point notation
%g %e or %f, whichever is shorter; (insignificant zeros do
not print)
-------------------------------------------------------------
Between the % and the conversion character (e, f, or g), you can add one or more of the following characters:
A minus sign (-) to specify left adjustment of the converted argument in its field
A digit string to specify a minimum field width
A period to separate the field width from the next digit string
A digit string specifying the precision (i.e., the number of digits to the right of the decimal point)
For more information about format strings, refer to the printf() and fprintf() routines in a C language reference manual.
fprintf differs from its C language fprintf() namesake in an important respect - it is vectorized for the case when input matrix A is nonscalar. The format string is recycled through the elements of A (columnwise) until all the elements are used up. It is then recycled in a similar manner, without reinitializing, through any additional matrix arguments.
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 2.71828183
The 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 quote in a string (the format command), use two single quotes together. For example,
fprint(1,'It''s Friday\n')
displays the following line on the screen:
It's Friday
The command
B = [8.8 7.7; 8800 7700]
fprintf(1,'X is %6.2f meters or %8.3f mm\n',9.9,9900,B)
displays 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 mm
fclose, ferror, fopen, fread, fscanf, fseek, ftell, fwrite, sprintf
[1] B.W. Kernighan and D.M. Ritchie, The C Programming Language, Prentice Hall, Inc., 1978.
(c) Copyright 1994 by The MathWorks, Inc.