PRINTF(3S-BSD) RISC/os Reference Manual PRINTF(3S-BSD)
NAME
printf, fprintf, sprintf, vprintf, vfprintf, vsprintf - for-
matted output conversion
SYNOPSIS
#include <stdio.h>
printf(format [, arg ] ... )
char *format;
fprintf(stream, format [, arg ] ... )
FILE *stream;
char *format;
char *sprintf(s, format [, arg ] ... )
char *s, *format;
#include <varargs.h>
vprintf(format, args)
char *format;
va_list args;
vfprintf(stream, format, args)
FILE *stream;
char *format;
va_list args;
vsprintf(s, format, args)
char *s, *format;
va_list args;
DESCRIPTION
printf places output on the standard output stream stdout.
fprintf places output on the named output stream. sprintf
places `output' in the string s, followed by the character
`\0'. Alternate forms, in which the arguments have already
been captured using the variable-length argument facilities
of varargs(3), are available under the names vprintf,
vfprintf, and vsprintf.
Each of these functions converts, formats, and prints its
arguments after the first under control of the first argu-
ment. The first argument is a character string which con-
tains two types of objects: plain characters, which are
simply copied to the output stream, and conversion specifi-
cations, each of which causes conversion and printing of the
next successive arg printf.
Each conversion specification is introduced by the character
%. The remainder of the conversion specification includes
in the following order:
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+ Zero or more of the following flags:
+ a `#' character specifying that the value should be
converted to an ``alternate form''. For c, d, s, and
u, conversions, this option has no effect. For o
conversions, the precision of the number is increased
to force the first character of the output string to a
zero. For x(X) conversion, a non-zero result has the
string 0x(0X) prepended 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 only appears in the results of those
conversions if a digit follows the decimal point).
For g and G conversions, trailing zeros are not
removed from the result as they would otherwise be;
+ a minus sign `-' which specifies left adjustment of
the converted value in the indicated field;
+ a `+' character specifying that there should always be
a sign placed before the number when using signed
conversions;
+ a space specifying that a blank should be left before
a positive number during a signed conversion. A `+'
overrides a space if both are used;
+ a zero `0' character indicating that zero-padding
should be used rather than blank-padding. A `-' over-
rides a `0' if both are used;
+ an optional digit string specifying a field width; if the
converted value has fewer characters than the field width
it will be blank-padded on the left (or right, if the
left-adjustment indicator has been given) to make up the
field width (note that a leading zero is a flag, but an
embedded zero is part of a field width);
+ an optional period, followed by an optional digit string
giving a precision which specifies the number of digits
to appear after the decimal point, for e- and f-
conversion, or the maximum number of characters to be
printed from a string; if the digit string is missing,
the precision is treated as zero;
+ the character l specifying that a following d, i, o, x,
or u corresponds to a long integer arg, or that a follow-
ing n corresponds to a pointer to a long integer arg;
+ a character which indicates the type of conversion to be
applied.
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A field width or precision may be `*' instead of a digit
string. In this case an integer arg supplies the field
width or precision.
The conversion characters and their meanings are:
dox The integer arg is converted to signed decimal,
unsigned octal, or unsigned hexadecimal notation
respectively.
i An alias for `d'.
f The float or double arg is converted to decimal nota-
tion in the style `[-]ddd.ddd' where the number of d's
after the decimal point is equal to the precision
specification for the argument. If the precision is
missing, 6 digits are given; if the precision is expli-
citly 0, no digits and no decimal point are printed.
eE 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 after is equal to the pre-
cision specification for the argument; when the preci-
sion is missing, 6 digits are produced. An uppercase E
is used for `E' conversion.
gG The float or double arg is printed in style f or in
style e (E) whichever gives full precision in minimum
space.
c The character arg is printed.
s arg is taken to be a string (character pointer) and
characters from the string are printed until a null
character or until the number of characters indicated
by the precision specification is reached; however if
the precision is 0 or missing all characters up to a
null are printed.
u The unsigned integer arg is converted to decimal and
printed (the result will be in the range 0 through MAX-
UINT, where MAXUINT equals 4294967295 on a MIPS R2000).
n arg is taken to be a pointer to an integer (possibly
long) through which is stored the number of characters
written to the output stream (or string) so far by this
call to printf (or fprintf, etc.).
p Arg is taken to be a pointer to void; it is printed in
style x.
% Print a `%'; no argument is converted.
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In no case does a non-existent or small field width cause
truncation of a field; padding takes place only if the
specified field width exceeds the actual width. Characters
generated by printf are printed as by putc(3S).
RETURN VALUE
The functions all return EOF(-1) if an error occurred.
sprintf returns the first argument. vprintf, vfprintf, and
vsprintf return the number of characters printed.
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 %d, %02d:%02d", weekday, month, day,
hour, min);
To print pi to 5 decimals:
printf("pi = %.5f", 4*atan(1.0));
SEE ALSO
putc(3S), scanf(3S).
BUGS
The functions still supports %D, %O, and %U. Do not use
these formats, as they will be disappearing soon.
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