Each conversion specifier may contain up to six different parts: an XPG3 position specifier, a set of flags, a minimum field width, a precision, a length modifier, and a conversion character. Any of these fields may be omitted except for the conversion character. The fields that are present must appear in the order given above. The paragraphs below discuss each of these fields in turn.

If the **%** is followed by a decimal number and a **$**, as in ``**%2$d**'', then the value to convert is not taken from the next sequential argument. Instead, it is taken from the argument indicated by the number, where 1 corresponds to the first *arg*. If the conversion specifier requires multiple arguments because of ***** characters in the specifier then successive arguments are used, starting with the argument given by the number. This follows the XPG3 conventions for positional specifiers. If there are any positional specifiers in *formatString* then all of the specifiers must be positional.

The second portion of a conversion specifier may contain any of the following flag characters, in any order:

**-**- Specifies that the converted argument should be left-justified in its field (numbers are normally right-justified with leading spaces if needed).

**+**- Specifies that a number should always be printed with a sign, even if positive.

*space*- Specifies that a space should be added to the beginning of the number if the first character isn't a sign.

**0**- Specifies that the number should be padded on the left with zeroes instead of spaces.

**#**- Requests an alternate output form. For
**o**and**O**conversions it guarantees that the first digit is always**0**. For**x**or**X**conversions,**0x**or**0X**(respectively) will be added to the beginning of the result unless it is zero. For all floatingpoint conversions (**e**,**E**,**f**,**g**, and**G**) it guarantees that the result always has a decimal point. For**g**and**G**conversions it specifies that trailing zeroes should not be removed.

The fourth portion of a conversion specifier is a precision, which consists of a period followed by a number. The number is used in different ways for different conversions. For **e**, **E**, and **f** conversions it specifies the number of digits to appear to the right of the decimal point. For **g** and **G** conversions it specifies the total number of digits to appear, including those on both sides of the decimal point (however, trailing zeroes after the decimal point will still be omitted unless the **#** flag has been specified). For integer conversions, it specifies a minimum number of digits to print (leading zeroes will be added if necessary). For **s** conversions it specifies the maximum number of characters to be printed; if the string is longer than this then the trailing characters will be dropped. If the precision is specified with ***** rather than a number then the next argument to the **format** command determines the precision; it must be a numeric string.

The fifth part of a conversion specifier is a length modifier, which must be **h** or **l**. If it is **h** it specifies that the numeric value should be truncated to a 16-bit value before converting. This option is rarely useful. The **l** modifier is ignored.

The last thing in a conversion specifier is an alphabetic character that determines what kind of conversion to perform. The following conversion characters are currently supported:

**d**- Convert integer to signed decimal string.

**u**- Convert integer to unsigned decimal string.

**i**- Convert integer to signed decimal string; the integer may either be in decimal, in octal (with a leading
**0**) or in hexadecimal (with a leading**0x**).

**o**- Convert integer to unsigned octal string.

**x**or**X**- Convert integer to unsigned hexadecimal string, using digits ``0123456789abcdef'' for
**x**and ``0123456789ABCDEF'' for**X**).

**c**- Convert integer to the 8-bit character it represents.

**s**- No conversion; just insert string.

**f**- Convert floating-point number to signed decimal string of the form
*xx*.*yyy*, where the number of*y*'s is determined by the precision (default: 6). If the precision is 0 then no decimal point is output.

**e**or**e**- Convert floating-point number to scientific notation in the form
*x*.*yyye±*z*z*, where the number of*y*'s is determined by the precision (default: 6). If the precision is 0 then no decimal point is output. If the**E**form is used then**E**is printed instead of**e**.

**g**or**G**- If the exponent is less than -4 or greater than or equal to the precision, then convert floatingpoint number as for
**%e**or**%E**. Otherwise convert as for**%f**. Trailing zeroes and a trailing decimal point are omitted.

**%**- No conversion: just insert
**%**.

[1] **%p** and **%n** specifiers are not currently supported.

[2] For **%c** conversions the argument must be a decimal string, which will then be converted to the corresponding character value.

[3] The **l** modifier is ignored; integer values are always converted as if there were no modifier present and real values are always converted as if the **l** modifier were present (i.e. type **double** is used for the internal representation). If the **h** modifier is specified then integer values are truncated to **short** before conversion.