|'#'||The value should be converted to an "alternate form". For c, d, i, n, p, 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 output string to a zero (except if a zero value is printed with an explicit precision of zero). For x and X conversions, a non-zero result has the string 0x (or 0X for X conversions) prepended to it. For a, A, e, E, f, F, g, and G conversions, the result will always contain a decimal point, even if no digits follow it (normally, a decimal point appears in the results of those conversions only if a digit follows). For g and G conversions, trailing zeros are not removed from the result as they would otherwise be.|
|'0(zero)'||Zero padding. For all conversions except n, the converted value is padded on the left with zeros rather than blanks. If a precision is given with a numeric conversion ( d, i, o, u, i, x, and X), the 0 flag is ignored.|
|'-'||A negative field width flag; the converted value is to be left adjusted on the field boundary. Except for n conversions, the converted value is padded on the right with blanks, rather than on the left with blanks or zeros. A - overrides a 0 if both are given.|
|' (space)'||A blank should be left before a positive number produced by a signed conversion ( a, A, d, e, E, f, F, g, G, or i).|
|'+'||A sign must always be placed before a number produced by a signed conversion. A + overrides a space if both are used.|
|''||Decimal conversions ( d, u, or i) or the integral portion of a floating point conversion ( f or F) should be grouped and separated by thousands using the non-monetary separator returned by localeconv(3).|
| Modifier d, i o, u, x, X n
hh Vt signed char Vt unsigned char Vt signed char *
h Vt short Vt unsigned short Vt short *
l (ell) Vt long Vt unsigned long Vt long *
ll (ell ell) Vt long long Vt unsigned long long Vt long long *
j Vt intmax_t Vt uintmax_t Vt intmax_t *
t Vt ptrdiff_t (see note) Vt ptrdiff_t *
z (see note) Vt size_t (see note)
q (deprecated) Vt quad_t Vt u_quad_t Vt quad_t *
modifier, when applied to a
o, u, x,
conversion, indicates that the argument is of an unsigned type
equivalent in size to a
.Vt ptrdiff_t . The z modifier, when applied to a d or i conversion, indicates that the argument is of a signed type equivalent in size to a
.Vt size_t . Similarly, when applied to an n conversion, it indicates that the argument is a pointer to a signed type equivalent in size to a
.Vt size_t .
The following length modifier is valid for the a, A, e, E, f, F, g, or G conversion:
| Modifier a, A, e, E, f, F, g, G
L Vt long double
The following length modifier is valid for the c or s conversion:
| Modifier c s
l (ell) Vt wint_t Vt wchar_t *
A field width or precision, or both, may be indicated by
or an asterisk followed by one or more decimal digits and a
instead of a
In this case, an
.Vt int argument supplies the field width or precision. A negative field width is treated as a left adjustment flag followed by a positive field width; a negative precision is treated as though it were missing. If a single format directive mixes positional (nn$) and non-positional arguments, the results are undefined.
The conversion specifiers and their meanings are:
.Vt int (or appropriate variant) argument is converted to signed decimal ( d and i), unsigned octal (o), unsigned decimal (u), or unsigned hexadecimal ( x and X) notation. The letters "abcdef" are used for x conversions; the letters "ABCDEF" are used for X conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros.
.Vt long int argument is converted to signed decimal, unsigned octal, or unsigned decimal, as if the format had been ld, lo, or lu respectively. These conversion characters are deprecated, and will eventually disappear.
.Vt double argument is rounded and converted in the style
.Sm off [-d . ddd e ± dd]
.Sm on where there is one digit before the decimal-point character and the number of digits after it is equal to the precision; if the precision is missing, it is taken as 6; if the precision is zero, no decimal-point character appears. An E conversion uses the letter E (rather than e) to introduce the exponent. The exponent always contains at least two digits; if the value is zero, the exponent is 00.
For a, A, e, E, f, F, g, and G conversions, positive and negative infinity are represented as inf and -inf respectively when using the lowercase conversion character, and INF and -INF respectively when using the uppercase conversion character. Similarly, NaN is represented as nan when using the lowercase conversion, and NAN when using the uppercase conversion.
.Vt double argument is rounded and converted to decimal notation in the style
.Sm off [-ddd . ddd],
.Sm on where the number of digits after the decimal-point character is equal to the precision specification. If the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. If a decimal point appears, at least one digit appears before it.
.Vt double argument is converted in style f or e (or F or E for G conversions). The precision specifies the number of significant digits. If the precision is missing, 6 digits are given; if the precision is zero, it is treated as 1. Style e is used if the exponent from its conversion is less than -4 or greater than or equal to the precision. Trailing zeros are removed from the fractional part of the result; a decimal point appears only if it is followed by at least one digit.
.Vt double argument is converted to hexadecimal notation in the style
.Sm off [-0x h . hhhp[±d]],
.Sm on where the number of digits after the hexadecimal-point character is equal to the precision specification. If the precision is missing, it is taken as enough to exactly represent the floating-point number; if the precision is explicitly zero, no hexadecimal-point character appears. This is an exact conversion of the mantissa+exponent internal floating point representation; the
.Sm off [-0x h . hhh]
.Sm on portion represents exactly the mantissa; only denormalized mantissas have a zero value to the left of the hexadecimal point. The p is a literal character p; the exponent is preceded by a positive or negative sign and is represented in decimal, using only enough characters to represent the exponent. The A conversion uses the prefix "0X" (rather than "0x"), the letters "ABCDEF" (rather than "abcdef") to represent the hex digits, and the letter P (rather than p) to separate the mantissa and exponent.
|C||Treated as c with the l (ell) modifier.|
.Vt int argument is converted to an
.Vt unsigned char , then to a
.Vt wchar_t as if by btowc(3), and the resulting character is written.
(ell) modifier is used, the
|S||Treated as s with the l (ell) modifier.|
.Vt char * argument is expected to be a pointer to an array of character type (pointer to a string) containing a multibyte sequence. Characters from the array are converted to wide characters and written up to (but not including) a terminating NUL character; if a precision is specified, no more than the number specified are written. If a precision is given, no null character need be present; if the precision is not specified, or is greater than the size of the array, the array must contain a terminating NUL character.
(ell) modifier is used, the
.Vt void * pointer argument is printed in hexadecimal (as if by %#x or %#lx).
The number of characters written so far is stored into the
integer indicated by the
.Vt int * (or variant) pointer argument. No argument is converted.
|%||A % is written. No argument is converted. The complete conversion specification is %%.|
The decimal point character is defined in the programs locale (category LC_NUMERIC).
In no case does a non-existent or small field width cause truncation of a numeric field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result.
Subject to the caveats noted in the BUGS section of printf(3), the wprintf, fwprintf, swprintf, vwprintf, vfwprintf and vswprintf functions conform to -isoC-99.
Refer to printf(3).