Perl Pocket Reference, 4th Edition

Chapter 19. Structure Conversion

pack template, list

Packs the values in list into a sequence of bytes, using the specified template. Returns this sequence as a string.

unpack template, expr

Unpacks the sequence of bytes in expr into a list, using template.

template is a sequence of characters as follows:

a / A	Byte string, null-/space-padded
b / B	Bit string in ascending/descending order
c / C	Signed/unsigned byte value
d / D	Native double/long double
f / F	Native float/Perl internal float
h / H	Hex string, low/high nybble first
i / I	Signed/unsigned integer value
j / J	Perl internal integer/unsigned
l / L	Signed/unsigned long value
n / N	Short/long in network (big endian) byte order
p / P	Pointer to a null-terminated/fixed-length string
q / Q	Signed/unsigned quad value
s / S	Signed/unsigned short value
u / U	Uuencoded string/Unicode UTF-8 character code
v / V	Short/long in VAX (little endian) byte order
w	A BER compressed integer
x / X	Null byte (skip forward)/Back up a byte
Z / @	Null-terminated string/null fill to position

The size of an integer, as used by i and I, depends on the system architecture. Nybbles, bytes, shorts, longs, and quads are always exactly 4, 8, 16, 32, and 64 bits respectively. Characters s, S, l, and L may be followed by a ! to signify native shorts and longs instead. x and X may be followed by a ! to specify alignment.

Each character, or group of characters between parentheses, may be followed by a decimal number, optionally between [ and ], that will be used as a repeat count; an asterisk ...