The pack and unpack functions in Perl are two functions for transforming data into a user-defined template.
The pack and unpack functions are used to convert data to and from a sequence of bytes. This is useful when accessing data from the network, a file, or I/O.
The pack function evaluates the data in List and outputs a binary representation of that data according to Expr.
pack Expr, List
Expr: A character that is optionally followed by a number (e.g. A2). Each character defines how the next sequence of bits is to be interpreted, and the number following the character represents how many times the sequence should be repeated.List: The data that is converted into bytes.pack returns the bit representation of the data in List, interpreting it according to the rules defined in Expr.
The code below converts the integer into the ASCII character A. Expr is C, which means that pack should convert the next character to its ASCII representation in bits.
$bits = pack("C", 65);print "bits are $bits\n";
The unpack function evaluates the bitstream in List and interprets it according to Expr before outputting it.
pack Expr, List
Expr: A character that is optionally followed by a number (e.g. A2). Each character defines how the next sequence of bits is to be interpreted, and the number following the character represents how many times the sequence should be repeated.List: The data that is interpreted.unpack returns the representation of the bitstream in List according to the rules defined in Expr.
The code below converts the bitstream for ‘A’ into the integer . Expr is c, which means that unpack should convert the next sequence of bits as a signed character.
$var = unpack('c', pack('C', 65));print "VAR is $var";
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