perl unpack()函數

perl unpack()函數例子，unpack()函數實例代碼 - 解壓縮的二進製字符串STRING 使用模板TEMPLATE 中指定的格式字符串。

語法

unpack TEMPLATE, STRING

定義和用法

解壓縮的二進製字符串STRING 使用模板TEMPLATE 中指定的格式字符串。基本上包反轉操作，返回到所提供的格式，所述填充值的列表。

您也可以任何格式的字段的前綴％<數字>表示你想要一個16位的校驗和值的字符串，而不是值。

返回值

• 解壓後的值列表

下麵是表，它給出在TEMPLATE要使用的值。

Character	Description
a	ASCII character string padded with null characters
A	ASCII character string padded with spaces
b	String of bits, lowest first
B	String of bits, highest first
c	A signed character (range usually -128 to 127)
C	An unsigned character (usually 8 bits)
d	A double-precision floating-point number
f	A single-precision floating-point number
h	Hexadecimal string, lowest digit first
H	Hexadecimal string, highest digit first
i	A signed integer
I	An unsigned integer
l	A signed long integer
L	An unsigned long integer
n	A short integer in network order
N	A long integer in network order
p	A pointer to a string
s	A signed short integer
S	An unsigned short integer
u	Convert to uuencode format
v	A short integer in VAX (little-endian) order
V	A long integer in VAX order
x	A null byte
X	Indicates "go back one byte"
@	Fill with nulls (ASCII 0)

例子

#!/usr/bin/perl -w
#by www.gitbook.net

$bits = pack("c", 65);
# prints A, which is ASCII 65.
print "bits are $bits\n";
$bits = pack( "x" );
# $bits is now a null chracter.
print "bits are $bits\n";
$bits = pack( "sai", 255, "T", 30 );
# creates a seven charcter string on most computers'
print "bits are $bits\n";

@array = unpack( "sai", "$bits" );

#Array now contains three elements: 255, A and 47.
print "Array $array[0]\n";
print "Array $array[1]\n";
print "Array $array[2]\n";

這將產生以下結果：

bits are A
bits are
bits are �T
Array 255
Array T
Array 30