str.unpack(format) â anArray
Instance Public methods
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 (â*'') will use up all remaining elements.
The directives sSiIlL may each be followed by an underscore
(â_'') or exclamation mark (â!'')
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.
Integer | |
Directive | Returns | Meaning
-----------------------------------------------------------------
C | Integer | 8-bit unsigned (unsigned char)
S | Integer | 16-bit unsigned, native endian (uint16_t)
L | Integer | 32-bit unsigned, native endian (uint32_t)
Q | Integer | 64-bit unsigned, native endian (uint64_t)
| |
c | Integer | 8-bit signed (signed char)
s | Integer | 16-bit signed, native endian (int16_t)
l | Integer | 32-bit signed, native endian (int32_t)
q | Integer | 64-bit signed, native endian (int64_t)
| |
S_, S! | Integer | unsigned short, native endian
I, I_, I! | Integer | unsigned int, native endian
L_, L! | Integer | unsigned long, native endian
| |
s_, s! | Integer | signed short, native endian
i, i_, i! | Integer | signed int, native endian
l_, l! | Integer | signed long, native endian
| |
S> L> Q> | Integer | same as the directives without ">" except
s> l> q> | | big endian
S!> I!> | | (available since Ruby 1.9.3)
L!> Q!> | | "S>" is same as "n"
s!> i!> | | "L>" is same as "N"
l!> q!> | |
| |
S< L< Q< | Integer | same as the directives without "<" except
s< l< q< | | little endian
S!< I!< | | (available since Ruby 1.9.3)
L!< Q!< | | "S<" is same as "v"
s!< i!< | | "L<" is same as "V"
l!< q!< | |
| |
n | Integer | 16-bit unsigned, network (big-endian) byte order
N | Integer | 32-bit unsigned, network (big-endian) byte order
v | Integer | 16-bit unsigned, VAX (little-endian) byte order
V | Integer | 32-bit unsigned, VAX (little-endian) byte order
| |
U | Integer | UTF-8 character
w | Integer | BER-compressed integer (see Array.pack)
Float | |
Directive | Returns | Meaning
-----------------------------------------------------------------
D, d | Float | double-precision, native format
F, f | Float | single-precision, native format
E | Float | double-precision, little-endian byte order
e | Float | single-precision, little-endian byte order
G | Float | double-precision, network (big-endian) byte order
g | Float | single-precision, network (big-endian) byte order
String | |
Directive | Returns | Meaning
-----------------------------------------------------------------
A | String | arbitrary binary string (remove trailing nulls and ASCII spaces)
a | String | arbitrary binary string
Z | String | null-terminated string
B | String | bit string (MSB first)
b | String | bit string (LSB first)
H | String | hex string (high nibble first)
h | String | hex string (low nibble first)
u | String | UU-encoded string
M | String | quoted-printable, MIME encoding (see RFC2045)
m | String | base64 encoded string (RFC 2045) (default)
| | base64 encoded string (RFC 4648) if followed by 0
P | String | pointer to a structure (fixed-length string)
p | String | pointer to a null-terminated string
Misc. | |
Directive | Returns | Meaning
-----------------------------------------------------------------
@ | --- | skip to the offset given by the length argument
X | --- | skip backward one byte
x | --- | skip forward one byte
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