(octave.info)Formatted Output

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14.2.4 Formatted Output
-----------------------

This section describes how to call ‘printf’ and related functions.

   The following functions are available for formatted output.  They are
modeled after the C language functions of the same name, but they
interpret the format template differently in order to improve the
performance of printing vector and matrix values.

   Implementation Note: For compatibility with MATLAB, escape sequences
in the template string (e.g., "\n" => newline) are expanded even when
the template string is defined with single quotes.

 -- : printf (TEMPLATE, ...)
     Print optional arguments under the control of the template string
     TEMPLATE to the stream ‘stdout’ and return the number of characters
     printed.

     See the Formatted Output section of the GNU Octave manual for a
     complete description of the syntax of the template string.

     Implementation Note: For compatibility with MATLAB, escape
     sequences in the template string (e.g., "\n" => newline) are
     expanded even when the template string is defined with single
     quotes.

     See also: Note: fprintf, Note: sprintf,
     Note: scanf.

 -- : fprintf (FID, TEMPLATE, ...)
 -- : fprintf (TEMPLATE, ...)
 -- : NUMBYTES = fprintf (...)
     This function is equivalent to ‘printf’, except that the output is
     written to the file descriptor FID instead of ‘stdout’.

     If FID is omitted, the output is written to ‘stdout’ making the
     function exactly equivalent to ‘printf’.

     The optional output returns the number of bytes written to the
     file.

     Implementation Note: For compatibility with MATLAB, escape
     sequences in the template string (e.g., "\n" => newline) are
     expanded even when the template string is defined with single
     quotes.

     See also: Note: fputs, Note: fdisp, Note:
     fwrite, Note: fscanf, *note printf:
     XREFprintf, Note: sprintf, Note: fopen.

 -- : sprintf (TEMPLATE, ...)
     This is like ‘printf’, except that the output is returned as a
     string.

     Unlike the C library function, which requires you to provide a
     suitably sized string as an argument, Octave’s ‘sprintf’ function
     returns the string, automatically sized to hold all of the items
     converted.

     Implementation Note: For compatibility with MATLAB, escape
     sequences in the template string (e.g., "\n" => newline) are
     expanded even when the template string is defined with single
     quotes.

     See also: Note: printf, Note: fprintf,
     Note: sscanf.

   The ‘printf’ function can be used to print any number of arguments.
The template string argument you supply in a call provides information
not only about the number of additional arguments, but also about their
types and what style should be used for printing them.

   Ordinary characters in the template string are simply written to the
output stream as-is, while “conversion specifications” introduced by a
‘%’ character in the template cause subsequent arguments to be formatted
and written to the output stream.  For example,

     pct = 37;
     filename = "foo.txt";
     printf ("Processed %d%% of '%s'.\nPlease be patient.\n",
             pct, filename);

produces output like

     Processed 37% of 'foo.txt'.
     Please be patient.

   This example shows the use of the ‘%d’ conversion to specify that a
scalar argument should be printed in decimal notation, the ‘%s’
conversion to specify printing of a string argument, and the ‘%%’
conversion to print a literal ‘%’ character.

   There are also conversions for printing an integer argument as an
unsigned value in octal, decimal, or hexadecimal radix (‘%o’, ‘%u’, or
‘%x’, respectively); or as a character value (‘%c’).

   Floating-point numbers can be printed in normal, fixed-point notation
using the ‘%f’ conversion or in exponential notation using the ‘%e’
conversion.  The ‘%g’ conversion uses either ‘%e’ or ‘%f’ format,
depending on what is more appropriate for the magnitude of the
particular number.

   You can control formatting more precisely by writing “modifiers”
between the ‘%’ and the character that indicates which conversion to
apply.  These slightly alter the ordinary behavior of the conversion.
For example, most conversion specifications permit you to specify a
minimum field width and a flag indicating whether you want the result
left- or right-justified within the field.

   The specific flags and modifiers that are permitted and their
interpretation vary depending on the particular conversion.  They’re all
described in more detail in the following sections.