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gawk: Nondecimal-numbers

 
 6.1.1.2 Octal and Hexadecimal Numbers
 .....................................
 
 In 'awk', all numbers are in decimal (i.e., base 10).  Many other
 programming languages allow you to specify numbers in other bases, often
 octal (base 8) and hexadecimal (base 16).  In octal, the numbers go 0,
 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, and so on.  Just as '11' in decimal is
 1 times 10 plus 1, so '11' in octal is 1 times 8 plus 1.  This equals 9
 in decimal.  In hexadecimal, there are 16 digits.  Because the everyday
 decimal number system only has ten digits ('0'-'9'), the letters 'a'
 through 'f' represent the rest.  (Case in the letters is usually
 irrelevant; hexadecimal 'a' and 'A' have the same value.)  Thus, '11' in
 hexadecimal is 1 times 16 plus 1, which equals 17 in decimal.
 
    Just by looking at plain '11', you can't tell what base it's in.  So,
 in C, C++, and other languages derived from C, there is a special
 notation to signify the base.  Octal numbers start with a leading '0',
 and hexadecimal numbers start with a leading '0x' or '0X':
 
 '11'
      Decimal value 11
 
 '011'
      Octal 11, decimal value 9
 
 '0x11'
      Hexadecimal 11, decimal value 17
 
    This example shows the difference:
 
      $ gawk 'BEGIN { printf "%d, %d, %d\n", 011, 11, 0x11 }'
      -| 9, 11, 17
 
    Being able to use octal and hexadecimal constants in your programs is
 most useful when working with data that cannot be represented
 conveniently as characters or as regular numbers, such as binary data of
 various sorts.
 
    'gawk' allows the use of octal and hexadecimal constants in your
 program text.  However, such numbers in the input data are not treated
 differently; doing so by default would break old programs.  (If you
 really need to do this, use the '--non-decimal-data' command-line
 option; ⇒Nondecimal Data.)  If you have octal or hexadecimal
 data, you can use the 'strtonum()' function (⇒String Functions)
 to convert the data into a number.  Most of the time, you will want to
 use octal or hexadecimal constants when working with the built-in
 bit-manipulation functions; see ⇒Bitwise Functions for more
 information.
 
    Unlike in some early C implementations, '8' and '9' are not valid in
 octal constants.  For example, 'gawk' treats '018' as decimal 18:
 
      $ gawk 'BEGIN { print "021 is", 021 ; print 018 }'
      -| 021 is 17
      -| 18
 
    Octal and hexadecimal source code constants are a 'gawk' extension.
 If 'gawk' is in compatibility mode (⇒Options), they are not
 available.
 
               A Constant's Base Does Not Affect Its Value
 
    Once a numeric constant has been converted internally into a number,
 'gawk' no longer remembers what the original form of the constant was;
 the internal value is always used.  This has particular consequences for
 conversion of numbers to strings:
 
      $ gawk 'BEGIN { printf "0x11 is <%s>\n", 0x11 }'
      -| 0x11 is <17>
 
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