NAME
printf, fprintf, sprintf, snprintf, vprintf, vfprintf,
vsprintf, vsnprintf - formatted output conversion
SYNOPSIS
#include <sys/types.h>
#include <stdio.h>
#include <stdarg.h>
int printf(const char *format [, arg] ...);
int fprintf(FILE *stream, const char *format [, arg] ...);
int sprintf(char *s, const char *format [, arg] ...);
int snprintf(char *s, size_t n, const char *format [, arg] ...);
int vprintf(const char *format, va_list args);
int vfprintf(FILE *stream, const char *format, va_list args);
int vsprintf(char *s, const char *format, va_list args);
int vsnprintf(char *s, size_t n, const char *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'. Snprintf (Minix-vmd only) is like sprintf except that
no more than n-1 characters are written to s followed by a
`\0'.
The v*printf functions can be used to make functions like
the first four by using the stdarg(3) method to process the
argument.
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.
Each conversion specification is introduced by the character
%. The remainder of the conversion specification includes
in the following order
o Zero or more of following flags:
o 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 out-
put 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.
o a minus sign `-' which specifies left adjustment
of the converted value in the indicated field;
o a `+' character specifying that there should
always be a sign placed before the number when
using signed conversions.
o a space specifying that a blank should be left
before a positive number during a signed conver-
sion. A `+' overrides a space if both are used.
o 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; if the field width begins with a
zero, zero-padding will be done instead of blank-
padding;
o an optional period `.' which serves to separate the
field width from the next digit string;
o an optional digit string specifying 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;
o the character l specifying that a following d, o, x, or
u corresponds to a long integer arg.
o a character which indicates the type of conversion to
be applied.
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 decimal, octal, or hex-
adecimal notation respectively.
X Like x, but use upper case instead of lower case.
f The float or double arg is converted to decimal
notation 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.
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 after is equal to the pre-
cision specification for the argument; when the preci-
sion is missing, 6 digits are produced.
g The float or double arg is printed in style d, in style
f, or in style 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.
% Print a `%'; no argument is converted.
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 by putc(3).
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(3), scanf(3), ecvt(3), stdarg(3).