perl中pack函数的实例

$foo = pack("WWWW",65,66,67,68);

# foo eq "ABCD"

$foo = pack("W4",65,66,67,68);

# same thing

$foo = pack("W4",0x24b6,0x24b7,0x24b8,0x24b9);

# same thing with Unicode circled letters.

$foo = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);

# same thing with Unicode circled letters. You don't get the UTF-8

# bytes because the U at the start of the format caused a switch to

# U0-mode, so the UTF-8 bytes get joined into characters

$foo = pack("C0U4",0x24b6,0x24b7,0x24b8,0x24b9);

# foo eq "/xe2/x92/xb6/xe2/x92/xb7/xe2/x92/xb8/xe2/x92/xb9"

# This is the UTF-8 encoding of the string in the previous example

$foo = pack("ccxxcc",65,66,67,68);

# foo eq "AB/0/0CD"

# NOTE: The examples above featuring "W" and "c" are true

# only on ASCII and ASCII-derived systems such as ISO Latin 1

# and UTF-8. On EBCDIC systems, the first example would be

# $foo = pack("WWWW",193,194,195,196);

$foo = pack("s2",1,2);

# "/1/0/2/0" on little-endian

# "/0/1/0/2" on big-endian

$foo = pack("a4","abcd","x","y","z");

# "abcd"

$foo = pack("aaaa","abcd","x","y","z");

# "axyz"

$foo = pack("a14","abcdefg");

# "abcdefg/0/0/0/0/0/0/0"

$foo = pack("i9pl", gmtime);

# a real struct tm (on my system anyway)

$utmp_template = "Z8 Z8 Z16 L";

$utmp = pack($utmp_template, @utmp1);

# a struct utmp (BSDish)

@utmp2 = unpack($utmp_template, $utmp);

# "@utmp1" eq "@utmp2"

sub bintodec {

unpack("N", pack("B32", substr("0" x 32 . shift, -32)));

}

$foo = pack('sx2l', 12, 34);

# short 12, two zero bytes padding, long 34

$bar = pack('s@4l', 12, 34);

# short 12, zero fill to position 4, long 34

# $foo eq $bar

$baz = pack('s.l', 12, 4, 34);

# short 12, zero fill to position 4, long 34

$foo = pack('nN', 42, 4711);

# pack big-endian 16- and 32-bit unsigned integers

$foo = pack('S>L>', 42, 4711);

# exactly the same

$foo = pack('s<l<', -42, 4711);

# pack little-endian 16- and 32-bit signed integers

$foo = pack('(sl)<', -42, 4711);

# exactly the same