3.44 `printf', `fprintf', `asprintf', `sprintf', `snprintf'--format output
int printf(const char *FORMAT [, ARG, ...]);
int fprintf(FILE *FD, const char *FORMAT [, ARG, ...]);
int sprintf(char *STR, const char *FORMAT [, ARG, ...]);
int asprintf(char **STRP, const char *FORMAT [, ARG, ...]);
int snprintf(char *STR, size_t SIZE, const char *FORMAT [, ARG, ...]);
`fprintf', `asprintf', `sprintf' and `snprintf' are identical to
`printf', other than the destination of the formatted output: `fprintf'
sends the output to a specified file FD, while `asprintf' stores the
output in a dynamically allocated buffer, while `sprintf' stores the
output in the specified char array STR and `snprintf' limits number of
characters written to STR to at most SIZE (including terminating `0').
For `sprintf' and `snprintf', the behavior is undefined if the output
`*STR' overlaps with one of the arguments. For `asprintf', STRP points
to a pointer to char which is filled in with the dynamically allocated
buffer. FORMAT is a pointer to a charater string containing two types
of objects: ordinary characters (other than `%'), which are copied
unchanged to the output, and conversion specifications, each of which
is introduced by `%'. (To include `%' in the output, use `%%' in the
format string.) A conversion specification has the following form:
%[FLAGS][WIDTH][.PREC][SIZE][TYPE]
The fields of the conversion specification have the following
meanings:
* FLAGS
an optional sequence of characters which control output
justification, numeric signs, decimal points, trailing zeroes, and
octal and hex prefixes. The flag characters are minus (`-'), plus
(`+'), space ( ), zero (`0'), and sharp (`#'). They can appear in
any combination.
`-'
The result of the conversion is left justified, and the right
is padded with blanks. If you do not use this flag, the
result is right justified, and padded on the left.
`+'
The result of a signed conversion (as determined by TYPE)
will always begin with a plus or minus sign. (If you do not
use this flag, positive values do not begin with a plus sign.)
`" " (space)'
If the first character of a signed conversion specification
is not a sign, or if a signed conversion results in no
characters, the result will begin with a space. If the space
( ) flag and the plus (`+') flag both appear, the space flag
is ignored.
`0'
If the TYPE character is `d', `i', `o', `u', `x', `X', `e',
`E', `f', `g', or `G': leading zeroes, are used to pad the
field width (following any indication of sign or base); no
spaces are used for padding. If the zero (`0') and minus
(`-') flags both appear, the zero (`0') flag will be ignored.
For `d', `i', `o', `u', `x', and `X' conversions, if a
precision PREC is specified, the zero (`0') flag is ignored.
Note that `0' is interpreted as a flag, not as the beginning
of a field width.
`#'
The result is to be converted to an alternative form,
according to the next character:
`0'
increases precision to force the first digit of the
result to be a zero.
`x'
a non-zero result will have a `0x' prefix.
`X'
a non-zero result will have a `0X' prefix.
`e, E or f'
The result will always contain a decimal point even if
no digits follow the point. (Normally, a decimal point
appears only if a digit follows it.) Trailing zeroes
are removed.
`g or G'
same as `e' or `E', but trailing zeroes are not removed.
`all others'
undefined.
* WIDTH
WIDTH is an optional minimum field width. You can either specify
it directly as a decimal integer, or indirectly by using instead
an asterisk (`*'), in which case an `int' argument is used as the
field width. Negative field widths are not supported; if you
attempt to specify a negative field width, it is interpreted as a
minus (`-') flag followed by a positive field width.
* PREC
an optional field; if present, it is introduced with ``.'' (a
period). This field gives the maximum number of characters to
print in a conversion; the minimum number of digits of an integer
to print, for conversions with TYPE `d', `i', `o', `u', `x', and
`X'; the maximum number of significant digits, for the `g' and `G'
conversions; or the number of digits to print after the decimal
point, for `e', `E', and `f' conversions. You can specify the
precision either directly as a decimal integer or indirectly by
using an asterisk (`*'), in which case an `int' argument is used
as the precision. Supplying a negative precision is equivalent to
omitting the precision. If only a period is specified the
precision is zero. If a precision appears with any other
conversion TYPE than those listed here, the behavior is undefined.
* SIZE
`h', `l', and `L' are optional size characters which override the
default way that `printf' interprets the data type of the
corresponding argument. `h' forces the following `d', `i', `o',
`u', `x' or `X' conversion TYPE to apply to a `short' or `unsigned
short'. `h' also forces a following `n' TYPE to apply to a pointer
to a `short'. Similarily, an `l' forces the following `d', `i',
`o', `u', `x' or `X' conversion TYPE to apply to a `long' or
`unsigned long'. `l' also forces a following `n' TYPE to apply to
a pointer to a `long'. `l' with `c', `s' is equivalent to `C',
`S' respectively. If an `h' or an `l' appears with another
conversion specifier, the behavior is undefined. `L' forces a
following `e', `E', `f', `g' or `G' conversion TYPE to apply to a
`long double' argument. If `L' appears with any other conversion
TYPE, the behavior is undefined.
* TYPE
TYPE specifies what kind of conversion `printf' performs. Here is
a table of these:
`%'
prints the percent character (`%')
`c'
prints ARG as single character
`C'
prints wchar_t ARG as single multibyte character
`s'
prints characters until precision is reached or a null
terminator is encountered; takes a string pointer
`S'
converts wchar_t characters to multibyte output characters
until precision is reached or a null wchar_t terminator is
encountered; takes a wchar_t pointer
`d'
prints a signed decimal integer; takes an `int' (same as `i')
`i'
prints a signed decimal integer; takes an `int' (same as `d')
`o'
prints a signed octal integer; takes an `int'
`u'
prints an unsigned decimal integer; takes an `int'
`x'
prints an unsigned hexadecimal integer (using `abcdef' as
digits beyond `9'); takes an `int'
`X'
prints an unsigned hexadecimal integer (using `ABCDEF' as
digits beyond `9'); takes an `int'
`f'
prints a signed value of the form `[-]9999.9999'; takes a
floating-point number
`e'
prints a signed value of the form
`[-]9.9999e[+|-]999'; takes a floating-point number
`E'
prints the same way as `e', but using `E' to introduce the
exponent; takes a floating-point number
`g'
prints a signed value in either `f' or `e' form, based on
given value and precision--trailing zeros and the decimal
point are printed only if necessary; takes a floating-point
number
`G'
prints the same way as `g', but using `E' for the exponent if
an exponent is needed; takes a floating-point number
`n'
stores (in the same object) a count of the characters written;
takes a pointer to `int'
`p'
prints a pointer in an implementation-defined format. This
implementation treats the pointer as an `unsigned long' (same
as `Lu').
Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.
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