PRINTF
Section: Standard I/O Functions (3S)
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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 after the first
under control of the first argument.
The first argument is a character string
which contains
two types of objects:
plain characters, 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
%.
Following 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 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;
- -
-
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
corresponds to a long integer
arg.
(A capitalized conversion code accomplishes
the same thing.)
- -
-
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
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 precision 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.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- SEE ALSO
-
- BUGS
-
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Time: 10:17:17 GMT, December 28, 2024