(libc.info.gz) Numeric Input Conversions

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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 ( 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 ( 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', or '%d' conversion.
  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 '%o', '%u', and '%x' conversions match unsigned integers in
 octal, decimal, and hexadecimal radices, respectively.  The syntax that
 is recognized is the same as that for the 'strtoul' function (
 Parsing of Integers) with the appropriate value ('8', '10', or '16')
 for the BASE argument.
 
    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' and '%i'
 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', and '%G' input conversions are
 interchangeable.  They all match an optionally signed floating point
 number, in the same syntax as for the 'strtod' function ( 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 ( General
 Numeric).
 
    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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