PRINTF(3S) DOMAIN/IX SYS5 PRINTF(3S)
NAME
printf, fprintf, sprintf - print formatted output
USAGE
#include <stdio.h>
int printf(format [, arg ] ...)
char *format;
int 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, followed by the null character (\0), in con-
secutive bytes starting at *s; it is the user's responsibil-
ity to ensure that enough storage is available. Each func-
tion 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 plain characters, which are simply
copied to the output stream, and "conversion specifica-
tions," each of which fetches 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 decimal digit string specifying a minimum
field width. If the converted value has fewer characters
than the field width, it will be padded on the left (or
right, if the left-adjustment flag, described below, has
been given) to the field width. If the field width for
an s conversion is preceded by a zero, the string is
right adjusted with zero-padding on the left.
⊕ A precision that gives the minimum number of digits to
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PRINTF(3S) DOMAIN/IX SYS5 PRINTF(3S)
appear for the d, o, u, x, or X conversions, the number
of digits to appear after the decimal point for the e and
f conversions, the maximum number of significant digits
for the g conversion, or the maximum number of characters
to be printed from a string in s conversion. The preci-
sion takes the form of a period (.) followed by a decimal
digit string; a null digit string is treated as zero.
⊕ An optional l (lowercase L) specifying that a following
d, o, u, x, or X conversion character applies to a long
integer arg. An l before any other conversion character
is ignored.
A character that indicates the type of conversion to be
applied.
A field width or precision may be indicated by an asterisk
(*) instead of by a digit string. In this case, an integer
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 preci-
sion must appear before the arg (if any) to be converted.
FLAGS
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 -).
blank
If the first character of a signed conversion is not a
sign, a blank will be prefixed to the result. This
implies that if the blank and + flags both appear, the
blank flag will be ignored.
# This flag specifies that the value is to be converted
to an "alternate form." For c, d, s, and u conversions,
the flag has no effect. 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 conver-
sions only if a digit follows it). For g and G conver-
sions, trailing zeros will not be removed from the
result (as they normally are).
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PRINTF(3S) DOMAIN/IX SYS5 PRINTF(3S)
CONVERSION SPECIFICATIONS
The conversion characters and their meanings are:
d, o, u, x, X
The integer arg is converted to signed decimal,
unsigned octal, decimal, or hexadecimal notation (x and
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
zeros. (For compatibility with older versions, padding
with leading zeros may be specified by prepending a
zero to the field width. This does not imply an octal
value for the field width.) 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 nota-
tion in the style "[-]ddd.ddd", where the number of di-
gits after the decimal point is equal to the precision
specification. If the precision is missing, six digits
are output; if the precision is explicitly zero, no de-
cimal point appears.
e,E The float or double arg is converted in the style
[-]d.ddde+dd", where there is one digit before the de-
cimal 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 de-
cimal 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 preci-
sion. Trailing zeros are removed from the result; a
decimal point appears only if it is followed by a di-
git.
c The character arg is printed.
s The arg is taken to be a string (character pointer) and
characters from the string are printed until a null
character (\0) is encountered, or until the number of
characters indicated by the precision specification is
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PRINTF(3S) DOMAIN/IX SYS5 PRINTF(3S)
reached. If the precision is missing, it is taken to
be infinite, so all characters up to the first null
character are printed. A NULL value for arg will yield
undefined results.
% Print a %; (percent sign). No argument is converted.
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 %d, %d:%.2d", weekday, month, day, hour, min);
To print pi to 5 decimal places:
printf("pi = %.5f", 4 * atan(1.0));
RELATED INFORMATION
ecvt(3C), putc(3S), scanf(3S), stdio(3S)
PRINTF-4 Printed 12/4/86