term% cat index.txt PRINTF(3S) PRINTF(3S)
NAME
printf, fprintf, sprintf - formatted output conversion
SYNOPSIS
#include <stdio.h>
printf(format [, arg ] ... )
char *format;
fprintf(stream, format [, arg ] ... )
FILE *stream;
char *format;
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' in
the string s, followed by the character `\0'.
Each of these functions converts, formats, and prints its arguments af‐
ter the first under control of the first argument. The first argument
is a character string which contains two types of objects: plain char‐
acters, which are simply copied to the output stream, and conversion
specifications, each of which causes conversion and printing of the
next successive arg printf.
Each conversion specification is introduced by the character %. Fol‐
lowing the %, there may be
- an optional minus sign `-' which specifies left adjustment of
the converted value in the indicated field;
- an optional digit string specifying a field width; if the con‐
verted 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 in‐
stead of blank-padding;
- an optional period `.' which serves to separate the field width
from the next digit string;
- 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;
- the character l specifying that a following d, o, x, or u corre‐
sponds to a long integer arg. (A capitalized conversion code
accomplishes the same thing.)
- a character which indicates the type of conversion to be ap‐
plied.
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 hexadecimal
notation respectively.
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 preci‐
sion is explicitly 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 precision specification for the argument;
when the precision 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. Null characters are ignored.
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 to 65535).
% 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)
BUGS
Very wide fields (>128 characters) fail.
PRINTF(3S)