pr

Algorithms for Image Processing and Computer Vision Source Code

@c ----------------------------------------------------------------------
@node printf, stdio
@heading @code{printf}
@subheading Syntax

@example
#include <stdio.h>

int printf(const char *format, @dots{});
@end example

@subheading Description

Sends formatted output from the arguments (@dots{}) to @code{stdout}.

The format string contains regular characters to print, as well as
conversion specifiers, which begin with a percent symbol.  Each
conversion speficier contains the following fields:

@itemize @bullet

@item

an optional flag, which may alter the conversion:

@table @code

@item -

left-justify the field.

@item +

Force a @code{+} sign on positive numbers.

@item space

To leave a blank space where a plus or minus sign would have been. 

@item #

Alternate conversion - prefix octal numbers with @code{0}, hexadecimal
numbers with @code{0x} or @code{0X}, or force a trailing decimal point
if a floating point conversion would have omitted it. 

@item 0

To pad numbers with leading zeros.

@end table

@item

A field width specifier, which specifies the minimum width of the field. 
This may also be an asterisk (@code{*}), which means that the actual
width will be obtained from the next argument.  If the argument is
negative, it supplies a @code{-} flag and a positive width. 

@item

An optional decimal point and a precision.  This may also be an
asterisk, but a negative argument for it indicates a precision of zero. 
The precision specifies the minimum number of digits to print for an
integer, the number of fraction digits for a floating point number (max
for @code{g} or @code{G}, actual for others), or the maximum number of
characters for a string. 

@item

An optional conversion qualifier, which may be @code{h} to specify
@code{short}, @code{l} to specify long ints, or @code{L} to specify
long doubles.

@item

The conversion type specifier:

@table @code

@item c

A single character

@item d

A signed integer

@item D

A signed long integer

@item e
@itemx E

A floating point number (double or long double).  The exponent case matches
the specifier case.  The representation always has an exponent.

@item f

A floating point number (double or long double).  The representation
never has an exponent. 

@item g
@itemx G

A floating point number (double or long double).  The exponent case matches
the specifier case.  The representation has an exponent if it needs one.

@item i

A signed integer.

@item n

The next argument is a pointer to an integer, and the number of
characters generated so far is stored in that integer. 

@item o

A unsigned integer, printed in base 8 instead of base 10.

@item p

A pointer.  This is printed with an @code{x} specifier.

@item s

A @code{NULL}-terminated string.

@item u

An unsigned integer.

@item U

An unsigned long integer.

@item x
@itemx X

An unsigned integer, printed in base 16 instead of base 10.  The case of
the letters used matches the specifier case. 

@item %

A single percent symbol is printed.

@end table

@end itemize

@subheading Return Value

The number of characters written.

@subheading Example

@example
printf("%-3d %10.2f%% Percent of %s\n", index, per[index], name[index]);
@end example