unpack(p1) public

Decodes str (which may contain binary data) according to the format string, returning an array of each value extracted. The format string consists of a sequence of single-character directives, summarized in the table at the end of this entry. Each directive may be followed by a number, indicating the number of times to repeat with this directive. An asterisk (``*’’) will use up all remaining elements. The directives sSiIlL may each be followed by an underscore (``_'') to use the underlying platform’s native size for the specified type; otherwise, it uses a platform-independent consistent size. Spaces are ignored in the format string. See also Array#pack. 

   "abc \0\0abc \0\0".unpack('A6Z6')   #=> ["abc", "abc "]
   "abc \0\0".unpack('a3a3')           #=> ["abc", " \000\000"]
   "abc \0abc \0".unpack('Z*Z*')       #=> ["abc ", "abc "]
   "aa".unpack('b8B8')                 #=> ["10000110", "01100001"]
   "aaa".unpack('h2H2c')               #=> ["16", "61", 97]
   "\xfe\xff\xfe\xff".unpack('sS')     #=> [-2, 65534]
   "now=20is".unpack('M*')             #=> ["now is"]
   "whole".unpack('xax2aX2aX1aX2a')    #=> ["h", "e", "l", "l", "o"]

This table summarizes the various formats and the Ruby classes returned by each. 

   Format | Returns | Function
   -------+---------+-----------------------------------------
     A    | String  | with trailing nulls and spaces removed
   -------+---------+-----------------------------------------
     a    | String  | string
   -------+---------+-----------------------------------------
     B    | String  | extract bits from each character (msb first)
   -------+---------+-----------------------------------------
     b    | String  | extract bits from each character (lsb first)
   -------+---------+-----------------------------------------
     C    | Fixnum  | extract a character as an unsigned integer
   -------+---------+-----------------------------------------
     c    | Fixnum  | extract a character as an integer
   -------+---------+-----------------------------------------
     d,D  | Float   | treat sizeof(double) characters as
          |         | a native double
   -------+---------+-----------------------------------------
     E    | Float   | treat sizeof(double) characters as
          |         | a double in little-endian byte order
   -------+---------+-----------------------------------------
     e    | Float   | treat sizeof(float) characters as
          |         | a float in little-endian byte order
   -------+---------+-----------------------------------------
     f,F  | Float   | treat sizeof(float) characters as
          |         | a native float
   -------+---------+-----------------------------------------
     G    | Float   | treat sizeof(double) characters as
          |         | a double in network byte order
   -------+---------+-----------------------------------------
     g    | Float   | treat sizeof(float) characters as a
          |         | float in network byte order
   -------+---------+-----------------------------------------
     H    | String  | extract hex nibbles from each character
          |         | (most significant first)
   -------+---------+-----------------------------------------
     h    | String  | extract hex nibbles from each character
          |         | (least significant first)
   -------+---------+-----------------------------------------
     I    | Integer | treat sizeof(int) (modified by _)
          |         | successive characters as an unsigned
          |         | native integer
   -------+---------+-----------------------------------------
     i    | Integer | treat sizeof(int) (modified by _)
          |         | successive characters as a signed
          |         | native integer
   -------+---------+-----------------------------------------
     L    | Integer | treat four (modified by _) successive
          |         | characters as an unsigned native
          |         | long integer
   -------+---------+-----------------------------------------
     l    | Integer | treat four (modified by _) successive
          |         | characters as a signed native
          |         | long integer
   -------+---------+-----------------------------------------
     M    | String  | quoted-printable
   -------+---------+-----------------------------------------
     m    | String  | base64-encoded
   -------+---------+-----------------------------------------
     N    | Integer | treat four characters as an unsigned
          |         | long in network byte order
   -------+---------+-----------------------------------------
     n    | Fixnum  | treat two characters as an unsigned
          |         | short in network byte order
   -------+---------+-----------------------------------------
     P    | String  | treat sizeof(char *) characters as a
          |         | pointer, and  return \emph{len} characters
          |         | from the referenced location
   -------+---------+-----------------------------------------
     p    | String  | treat sizeof(char *) characters as a
          |         | pointer to a  null-terminated string
   -------+---------+-----------------------------------------
     Q    | Integer | treat 8 characters as an unsigned
          |         | quad word (64 bits)
   -------+---------+-----------------------------------------
     q    | Integer | treat 8 characters as a signed
          |         | quad word (64 bits)
   -------+---------+-----------------------------------------
     S    | Fixnum  | treat two (different if _ used)
          |         | successive characters as an unsigned
          |         | short in native byte order
   -------+---------+-----------------------------------------
     s    | Fixnum  | Treat two (different if _ used)
          |         | successive characters as a signed short
          |         | in native byte order
   -------+---------+-----------------------------------------
     U    | Integer | UTF-8 characters as unsigned integers
   -------+---------+-----------------------------------------
     u    | String  | UU-encoded
   -------+---------+-----------------------------------------
     V    | Fixnum  | treat four characters as an unsigned
          |         | long in little-endian byte order
   -------+---------+-----------------------------------------
     v    | Fixnum  | treat two characters as an unsigned
          |         | short in little-endian byte order
   -------+---------+-----------------------------------------
     w    | Integer | BER-compressed integer (see Array.pack)
   -------+---------+-----------------------------------------
     X    | ---     | skip backward one character
   -------+---------+-----------------------------------------
     x    | ---     | skip forward one character
   -------+---------+-----------------------------------------
     Z    | String  | with trailing nulls removed
          |         | upto first null with *
   -------+---------+-----------------------------------------
     @    | ---     | skip to the offset given by the
          |         | length argument
   -------+---------+-----------------------------------------
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