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16.2.8 Integer Conversions

This section describes the options for the `%d', `%i', `%o', `%u', `%x', and `%X' conversion specifications. These conversions print integers in various formats.

The `%d' and `%i' conversion specifications both print an numeric argument as a signed decimal number; while `%o', `%u', and `%x' print the argument as an unsigned octal, decimal, or hexadecimal number (respectively). The `%X' conversion specification is just like `%x' except that it uses the characters `ABCDEF' as digits instead of `abcdef'.

The following flags are meaningful:

Left-justify the result in the field (instead of the normal right-justification).
For the signed `%d' and `%i' conversions, print a plus sign if the value is positive.
` '
For the signed `%d' and `%i' conversions, if the result doesn't start with a plus or minus sign, prefix it with a space character instead. Since the `+' flag ensures that the result includes a sign, this flag is ignored if you supply both of them.
For the `%o' conversion, this forces the leading digit to be `0', as if by increasing the precision. For `%x' or `%X', this prefixes a leading `0x' or `0X' (respectively) to the result. This doesn't do anything useful for the `%d', `%i', or `%u' conversions.
Pad the field with zeros instead of spaces. The zeros are placed after any indication of sign or base. This flag is ignored if the `-' flag is also specified, or if a precision is specified.

If a precision is supplied, it specifies the minimum number of digits to appear; leading zeros are produced if necessary. If you don't specify a precision, the number is printed with as many digits as it needs. If you convert a value of zero with an explicit precision of zero, then no characters at all are produced.