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<HTML><HEAD><TITLE>Formatted Output</TITLE></HEAD><BODY BGCOLOR="#FFFFFF">
<H1><A NAME="Formatted Output">Formatted Output</A></H1><HR>
<P><B><A HREF="#Print Formats">Print Formats</A>
&#183; <A HREF="#Print Functions">Print Functions</A>
&#183; <A HREF="#Print Conversion Specifiers">Print Conversion
Specifiers</A>
</B></P>
<HR>
<P>Several library functions help you convert data values from
encoded internal representations to text sequences that are
generally readable by people. You provide a
<A HREF="#format string">format string</A> as the value of the
<CODE>format</CODE> argument to each of these functions, hence
the term <B>formatted output</B>. The functions fall
into two categories:</P>
<UL>
<LI>The <B><A NAME="byte print functions">byte print functions</A></B>
(declared in
<A HREF="stdio.html#&lt;stdio.h&gt;" tppabs="http://ccs.ucsd.edu/c/stdio.html#&lt;stdio.h&gt;"><CODE>&lt;stdio.h&gt;</CODE></A>)
convert internal representations to sequences of type <I>char,</I>
and help you compose such sequences for display:
<A HREF="stdio.html#fprintf" tppabs="http://ccs.ucsd.edu/c/stdio.html#fprintf">fprintf</A>,
<A HREF="stdio.html#printf" tppabs="http://ccs.ucsd.edu/c/stdio.html#printf">printf</A>,
<A HREF="stdio.html#sprintf" tppabs="http://ccs.ucsd.edu/c/stdio.html#sprintf">sprintf</A>,
<A HREF="stdio.html#vfprintf" tppabs="http://ccs.ucsd.edu/c/stdio.html#vfprintf">vfprintf</A>,
<A HREF="stdio.html#vprintf" tppabs="http://ccs.ucsd.edu/c/stdio.html#vprintf">vprintf</A>, and
<A HREF="stdio.html#vsprintf" tppabs="http://ccs.ucsd.edu/c/stdio.html#vsprintf">vsprintf</A>.
For these function, a format string is a
<A HREF="lib_over.html#multibyte string" tppabs="http://ccs.ucsd.edu/c/lib_over.html#multibyte string">multibyte string</A>
that begins and ends in the
<A HREF="charset.html#initial shift state" tppabs="http://ccs.ucsd.edu/c/charset.html#initial shift state">initial shift state</A>.
<LI>The <B><A NAME="wide print functions">wide print functions</A></B>
(declared in
<A HREF="wchar.html#&lt;wchar.h&gt;" tppabs="http://ccs.ucsd.edu/c/wchar.html#&lt;wchar.h&gt;"><CODE>&lt;wchar.h&gt;</CODE></A>
and hence added with
<B><A HREF="lib_over.html#Amendment 1" tppabs="http://ccs.ucsd.edu/c/lib_over.html#Amendment 1">Amendment 1</A></B>)
convert internal representations to sequences of type
<A HREF="stddef.html#wchar_t" tppabs="http://ccs.ucsd.edu/c/stddef.html#wchar_t"><CODE>wchar_t</CODE></A>,
and help you compose such sequences for display:
<A HREF="wchar.html#fwprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#fwprintf">fwprintf</A>,
<A HREF="wchar.html#swprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#swprintf">swprintf</A>,
<A HREF="wchar.html#wprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#wprintf">wprintf</A>,
<A HREF="wchar.html#vfwprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#vfwprintf">vfwprintf</A>,
<A HREF="wchar.html#vswprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#vswprintf">vswprintf</A>, and
<A HREF="wchar.html#vwprintf" tppabs="http://ccs.ucsd.edu/c/wchar.html#vwprintf">vwprintf</A>.
For these functions, a format string is a
<A HREF="lib_over.html#wide-character string" tppabs="http://ccs.ucsd.edu/c/lib_over.html#wide-character string">wide-character string</A>.
In the descriptions that follow, a wide character <CODE>wc</CODE>
from a format string or a stream is compared to a specific (byte)
character <CODE>c</CODE> as if by evaluating the expression
<CODE><A HREF="wchar.html#wctob" tppabs="http://ccs.ucsd.edu/c/wchar.html#wctob">wctob</A>(wc) == c</CODE>.
</UL>
<H2><A NAME="Print Formats">Print Formats</A></H2>
<P>A <B><A NAME="format string">format string</A></B> has the same
syntax for both the print functions and the
<A HREF="lib_scan.html#Formatted Input" tppabs="http://ccs.ucsd.edu/c/lib_scan.html#Formatted Input">scan functions</A>:</P>
<P><IMG SRC="format.gif" tppabs="http://ccs.ucsd.edu/c/gif/format.gif"></P>
<P>A format string consists of zero or more
<B><A NAME="conversion specification">conversion specifications</A></B>
interspersed with literal text and
<B><A NAME="white space">white space</A></B>.
White space is a sequence of one or more
characters <CODE>c</CODE> for which the call
<CODE><A HREF="ctype.html#isspace" tppabs="http://ccs.ucsd.edu/c/ctype.html#isspace">isspace</A>(c)</CODE> returns nonzero.
(The characters defined as white space can change when you change the
<A HREF="locale.html#LC_CTYPE" tppabs="http://ccs.ucsd.edu/c/locale.html#LC_CTYPE"><CODE>LC_CTYPE</CODE></A>
<A HREF="locale.html#locale category" tppabs="http://ccs.ucsd.edu/c/locale.html#locale category">locale category</A>.)
For the print functions, a conversion specification is one of the
<A HREF="#print conversion specification">
print conversion specifications</A> described below.</P>
<P>A print function scans the format string once from beginning
to end to determine what conversions to perform. Every print
function accepts a
<A HREF="stdarg.html#varying number of arguments" tppabs="http://ccs.ucsd.edu/c/stdarg.html#varying number of arguments">varying number
of arguments</A>, either directly or under control of an argument of type
<A HREF="stdarg.html#va_list" tppabs="http://ccs.ucsd.edu/c/stdarg.html#va_list"><CODE>va_list</CODE></A>.
Some print conversion specifications
in the format string use the next argument in the list.
A print function uses each successive argument no more than
once. Trailing arguments can be left unused.</P>
<P>In the description that follows:</P>
<UL>
<LI><B><A NAME="integer conversions">integer conversions</A></B> are the
<B><A NAME="conversion specifiers">conversion specifiers</A></B> that
end in <CODE>d</CODE>, <CODE>i</CODE>, <CODE>o</CODE>, <CODE>u</CODE>,
<CODE>x</CODE>, or <CODE>X</CODE>
<LI><B><A NAME="floating-point conversions">
floating-point conversions</A></B>
are the conversion specifiers
that end in <CODE>e</CODE>, <CODE>E</CODE>, <CODE>f</CODE>,
<CODE>g</CODE>, or <CODE>G</CODE>
</UL>
<H2><A NAME="Print Functions">Print Functions</A></H2>
<P>For the print functions, literal text or
<A HREF="#white space">white space</A> in a format
string generates characters that match the characters in the format
string. A
<B><A NAME="print conversion specification">
print conversion specification</A></B> typically generates characters
by converting the next argument value to a corresponding text sequence.
A print conversion specification has the format:</P>
<P><IMG SRC="print.gif" tppabs="http://ccs.ucsd.edu/c/gif/print.gif"></P>
<P>Following the percent character (<B><CODE>%</CODE></B>)
in the format string, you can write zero or more
<B><A NAME="format flag">format flags</A></B>:</P>
<UL>
<LI><B><CODE>-</CODE></B>
-- to left-justify a conversion
</UL>
<UL>
<LI><B><CODE>+</CODE></B>
-- to generate a plus sign for signed values that
are positive
<LI><B><CODE><I>space</I></CODE></B>
-- to generate a <CODE><I>space</I></CODE> for signed values
that have neither a plus nor a minus sign
<LI><B><CODE>#</CODE></B>
-- to prefix <CODE>0</CODE> on an <CODE>o</CODE> conversion,
to prefix <CODE>0x</CODE> on an <CODE>x</CODE> conversion,
to prefix <CODE>0X</CODE> on an <CODE>X</CODE> conversion,
or to generate a decimal point and fraction
digits that are otherwise suppressed on a floating-point conversion
<LI><B><CODE>0</CODE></B>
-- to pad a conversion with leading zeros after
any sign or prefix, in the absence of a minus (<CODE>-</CODE>)
format flag or a specified precision
</UL>
<P>Following any format flags, you can write a
<B><A NAME="print field width">field width</A></B> that
specifies the minimum number of characters to generate for the conversion.
Unless altered by a format flag,
the default behavior is to pad a short conversion
on the left with <CODE><I>space</I></CODE> characters.
If you write an asterisk (<B><CODE>*</CODE></B>)
instead of a decimal number for a field width, then a print
function takes the value of the next argument (which must be of type
<I>int</I>) as the field width. If the argument value is negative,
it supplies a <CODE>-</CODE> format flag
and its magnitude is the field width.</P>
<P>Following any field width, you can write a dot (<B><CODE>.</CODE></B>)
followed by a
<B><A NAME="precision">precision</A></B>
that specifies one of the following:
the minimum number of digits to generate on an integer conversion;
the number of fraction digits to generate on an <CODE>e</CODE>,
<CODE>E</CODE>, or <CODE>f</CODE> conversion;
the maximum number of significant digits to generate
on a <CODE>g</CODE> or <CODE>G</CODE> conversion; or the maximum number
of characters to generate from a
<A HREF="lib_over.html#C string" tppabs="http://ccs.ucsd.edu/c/lib_over.html#C string">C string</A>
on an <CODE>s</CODE> conversion.</P>
<P>If you write an <B><CODE>*</CODE></B> instead of
a decimal number for a precision,
a print function takes the value of the next argument (which must
be of type <I>int</I>) as the precision. If the argument value is
negative, the default precision applies. If you do not write either
an <CODE>*</CODE> or a decimal number following the dot, the precision
is zero.</P>
<H2><A NAME="Print Conversion Specifiers">
Print Conversion Specifiers</A></H2>
<P>Following any
<A HREF="#precision">precision</A>,
you must write a one-character <B>print conversion specifier</B>,
possibly preceded by a one-character qualifier.
Each combination determines the type required of the
next argument (if any) and how the library functions alter the argument
value before converting it to a text sequence.
The <A HREF="#integer conversions">integer</A> and
<A HREF="#floating-point conversions">
floating-point conversions</A> also determine
what base to use for the text representation.
If a conversion specifier requires a precision <I>p</I> and you do
not provide one in the format, then the conversion specifier chooses
a default value for the precision. The following table
lists all defined combinations and their properties.</P>
<PRE><B>
Conversion Argument Converted Default
Specifier Type Value Base Precision</B>
%c int x (unsigned char)x
%lc wint_t x wchar_t a[2] = {x}
%d int x (int)x 10 1
%hd int x (short)x 10 1
%ld long x (long)x 10 1
%e double x (double)x 10 6
%Le long double x (long double)x 10 6
%E double x (double)x 10 6
%E long double x (long double)x 10 6
%f double x (double)x 10 6
%Lf long double x (long double)x 10 6
%g double x (double)x 10 6
%Lg long double x (long double)x 10 6
%G double x (double)x 10 6
%LG long double x (long double)x 10 6
%i int x (int)x 10 1
%hi int x (short)x 10 1
%li long x (long)x 10 1
%n int *x
%hn short *x
%ln long *x
%o int x (unsigned int)x 8 1
%ho int x (unsigned short)x 8 1
%lo long x (unsigned long)x 8 1
%p void *x (void *)x
%s char x[] x[0]... <B>large</B>
%ls wchar_t x[] x[0]... <B>large</B>
%u int x (unsigned int)x 10 1
%hu int x (unsigned short)x 10 1
%lu long x (unsigned long)x 10 1
%x int x (unsigned int)x 16 1
%hx int x (unsigned short)x 16 1
%lx long x (unsigned long)x 16 1
%X int x (unsigned int)x 16 1
%hX int x (unsigned short)x 16 1
%lX long x (unsigned long)x 16 1
%% <B>none</B> '%'</PRE>
<P>The print conversion specifier determines any behavior not summarized
in this table. In the following descriptions, <I>p</I> is the precision.
Examples follow each of the print conversion specifiers.
A single conversion can generate up to 509 characters.</P>
<P>You write <B><A NAME="%c"><CODE>%c</CODE></A></B>
to generate a single character from the converted
value. For a
<A HREF="lib_file.html#wide stream" tppabs="http://ccs.ucsd.edu/c/lib_file.html#wide stream">wide stream</A>,
conversion of the character <CODE>x</CODE> occurs as if by calling
<CODE><A HREF="wchar.html#btowc" tppabs="http://ccs.ucsd.edu/c/wchar.html#btowc">btowc</A>(x)</CODE>. </P>
<PRE>
printf("%c", 'a') <B>generates a</B>
printf("&lt;%3c|%-3c&gt;", 'a', 'b') <B>generates &lt; a|b &gt;</B>
wprintf(L"%c", 'a') <B>generates (wide) btowc(a)</B></PRE>
<P>You write <B><A NAME="%lc"><CODE>%lc</CODE></A></B>
to generate a single character from the converted value.
Conversion of the character <CODE>x</CODE> occurs as if
it is followed by a null character in an array of two elements of type
<A HREF="stddef.html#wchar_t" tppabs="http://ccs.ucsd.edu/c/stddef.html#wchar_t"><CODE>wchar_t</CODE></A>
converted by the conversion specification
<A HREF="#%ls"><CODE>ls</CODE></A>.</P>
<PRE>
printf("%lc", L'a') <B>generates a</B>
wprintf(L"lc", L'a') <B>generates (wide) L'a'</B></PRE>
<P>You write <B><A NAME="%d"><CODE>%d</CODE></A></B>,
<B><A NAME="%i"><CODE>%i</CODE></A></B>,
<B><A NAME="%o"><CODE>%o</CODE></A></B>,
<B><A NAME="%u"><CODE>%u</CODE></A></B>,
<B><A NAME="%x"><CODE>%x</CODE></A></B>, or
<B><A NAME="%X"><CODE>%X</CODE></A></B> to generate
a possibly signed integer representation. <CODE>%d</CODE> or <CODE>%i</CODE>
specifies signed decimal representation, <CODE>%o</CODE>
unsigned octal, <CODE>%u</CODE> unsigned decimal,
<CODE>%x</CODE> unsigned hexadecimal using the digits <CODE>0-9</CODE>
and <CODE>a-f</CODE>, and <CODE>%X</CODE> unsigned
hexadecimal using the digits <CODE>0-9</CODE> and <CODE>A-F</CODE>.
The conversion generates at least <I>p</I> digits
to represent the converted value. If <I>p</I> is zero,
a converted value of zero generates no digits.</P>
<PRE>
printf("%d %o %x", 31, 31, 31) <B>generates 31 37 1f</B>
printf("%hu", 0xffff) <B>generates 65535</B>
printf("%#X %+d", 31, 31) <B>generates 0X1F +31</B></PRE>
<P>You write <B><A NAME="%e"><CODE>%e</CODE></A></B> or
<B><A NAME="%E"><CODE>%E</CODE></A></B> to generate a signed fractional
representation with an exponent. The generated text takes the form
<I>&#177;d.dddE&#177;dd</I>, where <I>&#177;</I> is either a plus or
minus sign, <I>d</I> is a decimal digit, the dot (<I>.</I>)
is the decimal point for the current
<A HREF="locale.html#locale" tppabs="http://ccs.ucsd.edu/c/locale.html#locale">locale</A>,
and <I>E</I> is either <CODE>e</CODE> (for <CODE>%e</CODE> conversion)
or <CODE>E</CODE> (for <CODE>%E</CODE> conversion).
The generated text has one integer digit,
a decimal point if <I>p</I> is nonzero or if you specify the <CODE>#</CODE>
format flag, <I>p</I> fraction digits, and at least two exponent digits.
The result is rounded. The value zero has a zero exponent.</P>
<PRE>
printf("%e", 31.4) <B>generates 3.140000e+01</B>
printf("%.2E", 31.4) <B>generates 3.14E+01</B></PRE>
<P>You write <B><A NAME="%f"><CODE>%f</CODE></A></B>
to generate a signed fractional representation
with no exponent. The generated text takes the form <I>&#177;d.ddd</I>,
where <I>&#177;</I> is either a plus or minus sign,
<I>d</I> is a decimal digit, and the dot (<I>.</I>)
is the decimal point for the current
<A HREF="locale.html#locale" tppabs="http://ccs.ucsd.edu/c/locale.html#locale">locale</A>.
The generated text has at least one integer digit,
a decimal point if <I>p</I> is nonzero or if you specify
the <CODE>#</CODE> format flag, and <I>p</I> fraction digits.
The result is rounded.</P>
<PRE>
printf("%f", 31.4) <B>generates 31.400000</B>
printf("%.0f %#.0f", 31.0, 31.0) <B>generates 31 31.</B></PRE>
<P>You write <B><A NAME="%g"><CODE>%g</CODE></A></B> or
<B><A NAME="%G"><CODE>%G</CODE></A></B> to generate a signed fractional
representation with or without an exponent, as appropriate.
For <CODE>%g</CODE> conversion, the generated text
takes the same form as either <CODE>%e</CODE>
or <CODE>%f</CODE> conversion. For <CODE>%G</CODE> conversion,
it takes the same form as either
<CODE>%E</CODE> or <CODE>%f</CODE> conversion.
The precision <I>p</I> specifies the number
of significant digits generated. (If <I>p</I> is zero, it is changed
to 1.) If <CODE>%e</CODE> conversion would yield an exponent in the range
[-4, <I>p</I>), then <CODE>%f</CODE> conversion occurs instead.
The generated text has no trailing zeros
in any fraction and has a decimal point
only if there are nonzero fraction digits, unless you specify the
<CODE>#</CODE> format flag.</P>
<PRE>
printf("%.6g", 31.4) <B>generates 31.4</B>
printf("%.1g", 31.4) <B>generates 3.14e+01</B></PRE>
<P>You write <B><A NAME="%n"><CODE>%n</CODE></A></B>
to store the number of characters generated
(up to this point in the format) in the object of type <I>int</I>
whose address is the value of the next successive argument.</P>
<PRE>
printf("abc%n", &amp;x) <B>stores 3</B></PRE>
<P>You write <B><A NAME="%p"><CODE>%p</CODE></A></B>
to generate an external representation of a <I>pointer to void.</I>
The conversion is implementation defined.</P>
<PRE>
printf("%p", (void *)&amp;x) <B>generates, e.g. F4C0</B></PRE>
<P>You write <B><A NAME="%s"><CODE>%s</CODE></A></B>
to generate a sequence of characters from
the values stored in the argument
<A HREF="lib_over.html#C string" tppabs="http://ccs.ucsd.edu/c/lib_over.html#C string">C string</A>. For a
<A HREF="lib_file.html#wide stream" tppabs="http://ccs.ucsd.edu/c/lib_file.html#wide stream">wide stream</A>, conversion
occurs as if by repeatedly calling
<A HREF="wchar.html#mbrtowc" tppabs="http://ccs.ucsd.edu/c/wchar.html#mbrtowc"><CODE>mbrtowc</CODE></A>,
beginning in the
<A HREF="charset.html#initial conversion state" tppabs="http://ccs.ucsd.edu/c/charset.html#initial conversion state">
initial conversion state</A>.
The conversion generates no more than <I>p</I> characters,
up to but not including the terminating null character.</P>
<PRE>
printf("%s", "hello") <B>generates hello</B>
printf("%.2s", "hello") <B>generates he</B>
wprintf(L"%s", "hello") <B>generates (wide) hello</B></PRE>
<P>You write <B><A NAME="%ls"><CODE>%ls</CODE></A></B>
to generate a sequence of characters from
the values stored in the argument
<A HREF="lib_over.html#wide-character string" tppabs="http://ccs.ucsd.edu/c/lib_over.html#wide-character string">wide-character string</A>.
For a <A HREF="lib_file.html#byte stream" tppabs="http://ccs.ucsd.edu/c/lib_file.html#byte stream">byte stream</A>,
conversion occurs as if by repeatedly calling
<A HREF="wchar.html#wcrtomb" tppabs="http://ccs.ucsd.edu/c/wchar.html#wcrtomb"><CODE>wcrtomb</CODE></A>, beginning in the
<A HREF="charset.html#initial conversion state" tppabs="http://ccs.ucsd.edu/c/charset.html#initial conversion state">
initial conversion state</A>,
so long as complete multibyte characters can be generated.
The conversion generates no more than
<I>p</I> characters, up to but not including the terminating null
character.</P>
<PRE>
printf("%ls", L"hello") <B>generates hello</B>
wprintf(L"%.2s", L"hello") <B>generates (wide) he</B></PRE>
<P>You write <B><A NAME="%%"><CODE>%%</CODE></A></B> to generate
the percent character (<CODE>%</CODE>).</P>
<PRE>
printf("%%") <B>generates %</B></PRE>
<HR>
<P>See also the
<B><A HREF="index.html#Table of Contents" tppabs="http://ccs.ucsd.edu/c/index.html#Table of Contents">Table of Contents</A></B> and the
<B><A HREF="_index.html" tppabs="http://ccs.ucsd.edu/c/_index.html">Index</A></B>.</P>
<P><I>
<A HREF="crit_pb.html" tppabs="http://ccs.ucsd.edu/c/crit_pb.html">Copyright</A> &#169; 1989-1996
by P.J. Plauger and Jim Brodie. All rights reserved.</I></P>
</BODY></HTML>

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