1.4.1. Problem

1.4.2. Solution

$num  = ord($char);
$char = chr($num);

The %c format used in printf and sprintf also converts a number to a character:

$char = sprintf("%c", $num);                # slower than chr($num)
printf("Number %d is character %c\n", $num, $num);
Number 101 is character e

A C* template used with pack and unpack can quickly convert many 8-bit bytes; similarly, use U* for Unicode characters.

@bytes = unpack("C*", $string);
$string = pack("C*", @bytes);

$unistr = pack("U4",0x24b6,0x24b7,0x24b8,0x24b9);
@unichars = unpack("U*", $unistr);

1.4.3. Discussion

$value     = ord("e");    # now 101
$character = chr(101);    # now "e"

printf("Number %d is character %c\n", 101, 101);

@ascii_character_numbers = unpack("C*", "sample");
print "@ascii_character_numbers\n";
115 97 109 112 108 101

$word = pack("C*", @ascii_character_numbers);
$word = pack("C*", 115, 97, 109, 112, 108, 101);   # same
print "$word\n";
sample

Here's how to convert from HAL to IBM:

$hal = "HAL";
@byte = unpack("C*", $hal);
foreach $val (@byte) {
    $val++;                 # add one to each byte value
}
$ibm = pack("C*", @byte);
print "$ibm\n";             # prints "IBM"

On single-byte character data, such as plain old ASCII or any of the various ISO 8859 charsets, the ord function returns numbers from 0 to 255. These correspond to C's unsigned char data type.

However, Perl understands more than that: it also has integrated support for Unicode, the universal character encoding. If you pass chr, sprintf "%c", or pack "U*" numeric values greater than 255, the return result will be a Unicode string.

Here are similar operations with Unicode:

@unicode_points = unpack("U*", "fac\x{0327}ade");
print "@unicode_points\n";
102 97 99 807 97 100 101

$word = pack("U*", @unicode_points);
print "$word\n";
façade

If all you're doing is printing out the characters' values, you probably don't even need to use unpack. Perl's printf and sprintf functions understand a v modifier that works like this:

printf "%vd\n", "fac\x{0327}ade";
102.97.99.807.97.100.101

printf "%vx\n", "fac\x{0327}ade";
66.61.63.327.61.64.65

The numeric value of each character (that is, its "code point" in Unicode parlance) in the string is emitted with a dot separator.

1.4.4. See Also