printf(3s) DG/UX 4.30 printf(3s)
NAME
printf, fprintf, sprintf - print formatted output
SYNOPSIS
#include <stdio.h>
int printf (format , arg ... )
char *format;
int fprintf (stream, format , arg ... )
FILE *stream;
char *format;
int sprintf (s, format [ , arg ] ... )
char *s, *format;
DESCRIPTION
printf places output on the standard output stream stdout.
Fprintf places output on the named output stream. Sprintf
places ``output,'' followed by the null character (\0), in
consecutive bytes starting at *s; it is the user's
responsibility to ensure that enough storage is available.
Each function returns the number of characters transmitted
(not including the \0 in the case of sprintf), or a negative
value if an output error was encountered.
Each of these functions converts, formats, and prints its
args under control of the format. The format is a character
string that contains two types of objects: plain
characters, which are simply copied to the output stream,
and conversion specifications, each of which results in
fetching of zero or more args. The results are undefined if
there are insufficient args for the format. If the format
is exhausted while args remain, the excess args are simply
ignored.
Each conversion specification is introduced by the character
%. After the %, the following appear in sequence:
Zero or more flags, which modify the meaning of the
conversion specification.
An optional minimum field width. If the converted
value has fewer characters than the field width, it
will be padded with spaces (by default) on the left (or
right, if the left-adjustment flag `-', described
below, has been given) to the field width. If the
field width digit string starts with a zero, padding is
with zeros. The field width takes the form of an
asterisk (*) (described later) or a decimal integer.
A precision that gives the minimum number of digits to
Licensed material--property of copyright holder(s) Page 1
printf(3s) DG/UX 4.30 printf(3s)
appear for the d, i, o, u, x, or X conversions, the
number of digits to appear after the decimal point for
the e, E, and f conversions, the maximum number of
significant digits for the g and G conversion, or the
maximum number of characters to be printed from a
string in s conversion. The precision takes the form
of a period (.) followed by an asterisk (*) (described
later) or a decimal digit string; a null digit string
is treated as zero. Padding specified by the
precision overrides the padding specified by the field
width.
An optional h specifying that a following d, i, o, u,
x, or X conversion character applies to a short int or
unsigned short int arg ( arg will have been promoted
according to integral promotions, and its value shall
be converted to short int or unsigned short int before
printing); an optional h specifying that a following n
conversion specifier applies to a pointer to a short
int arg; an optional l (ell) specifying that a
following d, i, o, u, x, or X conversion character
applies to a long int or unsigned long int arg; an
optional l specifying that the following n conversion
specifier applies to a pointer to a long int arg; or an
optional L specifying that a following e, E, f, g, or G
conversion specifier applies to a long double arg. An
h, l, or L before any other conversion specifier is
ignored.
A character that indicates the type of conversion to be
applied.
A field width, or precision, or both, may be indicated by an
asterisk (*) instead of a digit string. In this case, an
int arg supplies the field width or precision. The arg that
is actually converted is not fetched until the conversion
letter is seen, so the args specifying field width or
precision must appear (in that order) before the args (if
any) to be converted. A negative field width arg is taken
as a `-' flag followed by a positive field width. A negative
precision arg is taken as if the precision were omitted.
The flag characters and their meanings are:
- The result of the conversion will be left-
justified within the field.
+ The result of a signed conversion will always
begin with a sign (+ or -).
space If the first character of a signed conversion is
not a sign, a space will be prefixed to the
result. If the space and + flags both appear, the
Licensed material--property of copyright holder(s) Page 2
printf(3s) DG/UX 4.30 printf(3s)
space flag will be ignored.
# This flag specifies that the value is to be
converted to an ``alternate form.'' For o
conversion, it increases the precision to force
the first digit of the result to be a zero. For x
or X conversion, a non-zero result will have 0x or
0X prefixed to it. For e, E, f, g, and G
conversions, the result will always contain a
decimal point, even if no digits follow the point
(normally, a decimal point appears in the result
of these conversions only if a digit follows it).
For g and G conversions, trailing zeroes will not
be removed from the result (as they normally are).
For all other conversions, this flag has no
effect.
0 For d, i, o, u, x, X, e, E, f, g, and G
conversions, leading zeros (following any
indication of sign or base) are used to pad to the
field width; no white space padding is performed.
If the 0 and - flags both appear, the 0 flag will
be ignored. For d, i, o, u, x, and X conversions,
if a precision is specified, the 0 flag will be
ignored. For other conversions, the 0 flag will
be ignored.
The conversion characters and their meanings are:
d,i,o,u,x,X
The int arg is converted to signed decimal (d or
i), unsigned octal, (o), decimal (u), or
hexadecimal notation (x or X), respectively; the
letters abcdef are used for x conversion and the
letters ABCDEF for X conversion. The precision
specifies the minimum number of digits to appear;
if the value being converted can be represented in
fewer digits, it will be expanded with leading
zeroes. The default precision is 1. The result
of converting a zero value with a precision of
zero is a null string.
f The float or double arg is converted to decimal
notation in the style ``[-]ddd.ddd,'' where the
number of digits after the decimal point is equal
to the precision specification. If the precision
is missing, it is taken as 6; if the precision is
0, and the # flag is not specified, no decimal
point character appears. It a decimal point
appears, at least one digit appears before it.
The value is rounded to the appropriate number of
digits.
Licensed material--property of copyright holder(s) Page 3
printf(3s) DG/UX 4.30 printf(3s)
e,E The float or double arg is converted in the style
``[-]d.ddde+dd,'' where there is one digit before
the decimal point and the number of digits after
it is equal to the precision; when the precision
is missing, six digits are produced; if the
precision is zero, no decimal point appears. The
E format code will produce a number with E instead
of e introducing the exponent. The exponent
always contains at least two digits.
g,G The float or double arg is printed in style f or e
(or in style E in the case of a G format code),
with the precision specifying the number of
significant digits. The style used depends on the
value converted: style e will be used only if the
exponent resulting from the conversion is less
than -4 or greater than the precision. Trailing
zeroes are removed from the result; a decimal
point appears only if it is followed by a digit.
c The character arg is printed.
s The arg is taken to be a pointer to an array of
type char. Characters from the array are written
up to (but not including) a terminating null
character (\0); it the precision is specified, no
more than that many characters will be written.
If the precision is not specified or is greater
than the size of the array, the array shall
contain a null character. A NULL value for arg
will yield undefined results.
p The arg is taken as a pointer to void. The value
of the pointer is converted to an octal
representation.
n The arg shall be a pointer to an int into which is
written the number of characters written to the
output stream by this call to printf. No arg is
converted.
% Print a %; no argument is converted. The complete
conversion specification shall be %%.
In printing floating point types (float and double), if the
exponent is 0x7FF and the mantissa is not equal to zero,
then the output is
[-]NaN0xdddddddd
where 0xdddddddd is the hexadecimal representation of the
leftmost 32 bits of the mantissa. If the mantissa is zero,
Licensed material--property of copyright holder(s) Page 4
printf(3s) DG/UX 4.30 printf(3s)
the output is
[+]inf.
In no case does a non-existent or small field width cause
truncation of a field; if the result of a conversion is
wider than the field width, the field is simply expanded to
contain the conversion result. Characters generated by
printf and fprintf are printed as if putc(3S) had been
called.
EXAMPLES
To print a date and time in the form ``Sunday, July 3,
10:02,'' where weekday and month are pointers to null-
terminated strings:
printf("%s, %s %i, %d:%.2d", weekday, month, day, hour, min);
To print pi to 5 decimal places:
printf("pi = %.5f", 4 * atan(1.0));
SEE ALSO
ecvt(3), putc(3S), scanf(3S), stdio(3S).
Licensed material--property of copyright holder(s) Page 5