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#### 12.14.4 Numeric Input Conversions

This section describes the `scanf` conversions for reading numeric values.

The ‘%d’ conversion matches an optionally signed integer in decimal radix. The syntax that is recognized is the same as that for the `strtol` function (see Parsing of Integers) with the value `10` for the base argument.

The ‘%i’ conversion matches an optionally signed integer in any of the formats that the C language defines for specifying an integer constant. The syntax that is recognized is the same as that for the `strtol` function (see Parsing of Integers) with the value `0` for the base argument. (You can print integers in this syntax with `printf` by using the ‘#’ flag character with the ‘%x’, ‘%o’, ‘%b’, or ‘%d’ conversion. See Integer Conversions.)

For example, any of the strings ‘10’, ‘0xa’, or ‘012’ could be read in as integers under the ‘%i’ conversion. Each of these specifies a number with decimal value `10`.

The ‘%b’, ‘%o’, ‘%u’, and ‘%x’ conversions match unsigned integers in binary, octal, decimal, and hexadecimal radices, respectively. The syntax that is recognized is the same as that for the `strtoul` function (see Parsing of Integers) with the appropriate value (`2`, `8`, `10`, or `16`) for the base argument. The ‘%b’ conversion accepts an optional leading ‘0b’ or ‘0B’ in all standards modes.

The ‘%X’ conversion is identical to the ‘%x’ conversion. They both permit either uppercase or lowercase letters to be used as digits.

The default type of the corresponding argument for the `%d`, `%i`, and `%n` conversions is `int *`, and `unsigned int *` for the other integer conversions. You can use the following type modifiers to specify other sizes of integer:

hh

Specifies that the argument is a `signed char *` or ```unsigned char *```.

This modifier was introduced in ISO C99.

h

Specifies that the argument is a `short int *` or ```unsigned short int *```.

j

Specifies that the argument is a `intmax_t *` or `uintmax_t *`.

This modifier was introduced in ISO C99.

l

Specifies that the argument is a `long int *` or ```unsigned long int *```. Two ‘l’ characters is like the ‘L’ modifier, below.

If used with ‘%c’ or ‘%s’ the corresponding parameter is considered as a pointer to a wide character or wide character string respectively. This use of ‘l’ was introduced in Amendment 1 to ISO C90.

ll
L
q

Specifies that the argument is a `long long int *` or `unsigned long long int *`. (The `long long` type is an extension supported by the GNU C compiler. For systems that don’t provide extra-long integers, this is the same as `long int`.)

The ‘q’ modifier is another name for the same thing, which comes from 4.4 BSD; a `long long int` is sometimes called a “quad” `int`.

t

Specifies that the argument is a `ptrdiff_t *`.

This modifier was introduced in ISO C99.

z

Specifies that the argument is a `size_t *`.

This modifier was introduced in ISO C99.

All of the ‘%e’, ‘%f’, ‘%g’, ‘%E’, ‘%F’ and ‘%G’ input conversions are interchangeable. They all match an optionally signed floating point number, in the same syntax as for the `strtod` function (see Parsing of Floats).

For the floating-point input conversions, the default argument type is `float *`. (This is different from the corresponding output conversions, where the default type is `double`; remember that `float` arguments to `printf` are converted to `double` by the default argument promotions, but `float *` arguments are not promoted to `double *`.) You can specify other sizes of float using these type modifiers:

l

Specifies that the argument is of type `double *`.

L

Specifies that the argument is of type `long double *`.

For all the above number parsing formats there is an additional optional flag ‘'’. When this flag is given the `scanf` function expects the number represented in the input string to be formatted according to the grouping rules of the currently selected locale (see Generic Numeric Formatting Parameters).

If the `"C"` or `"POSIX"` locale is selected there is no difference. But for a locale which specifies values for the appropriate fields in the locale the input must have the correct form in the input. Otherwise the longest prefix with a correct form is processed.

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