Chapter 5:Perl One-Liners：Working with Arrays and Strings

In this chapter, we’ll look at various one-liners for

creating strings and arrays,
for doing things like generating passwords,
creating strings of certain length,
finding the numeric values of characters,
creating arrays of numbers.

You’ll also learn about the range operator .., the x operator, the $, special variable, and the @ARGV array.

5.1 Generate and print the alphabet

    perl -le 'print a..z'

The $, is the field separator. It’s output by print between each field. Semantically, though, using join to separate the list of letters with a comma is more appealing because it works even when not using print directly:

    perl -le '$alphabet = join ",", ("a".."z"); print $alphabet'

5.2 Generate and print all the strings from “a” to “zz”

5.3 Create a hex lookup table

perl -le '
$num = 255;
@hex = (0..9, "a".."f");
while ($num) {
$s = $hex[($num % 16)].$s;
$num = int $num/16;
}
print $s
'

But surely, converting a number to hex is much easier if I use printf(or sprintf) with the %x format specifier.

    perl -le 'printf("%x", 255)'

To convert the number back from hex to dec, use the hex operator:

    perl -le '$num = "ff"; print hex $num'

5.4 Generate a random eight-character password

        perl -le 'print map { ("a".."z")[rand 26] } 1..8'

5.5 Create a string of specific length

    perl -le 'print "a"x50'

For example, if you need 1KB of data, just
do this:

    perl -e 'print "a"x1024'

When you use the repetition operator in the list context, with a list as its first operand, you create a list with the given elements repeated, like this:

    perl -le '@list = (1,2)x20; print "@list"'

5.6 Create an array from a string

    @months = split ' ', "Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec"

5.7 Create a string from the command-line arguments

    perl -le 'print "(", (join ",", @ARGV), ")"' val1 val2 val3

5.8 Find the numeric values for characters in a string

    perl -le 'print join ", ", map { ord } split //, "hello world"'

You could also do this with the unpack operator by specifying C* as the unpacking template:

    perl -le 'print join ", ", unpack("C*", "hello world")'

5.9 Convert a list of numeric ASCII values into a string

perl -le '
@ascii = (99, 111, 100, 105, 110, 103);
print pack("C*", @ascii)
'

You can also use the @ARGV array and pass the ASCII values as arguments to the one-liner:

    perl -le 'print map chr, @ARGV' 99 111 100 105 110 103

5.10 Generate an array with odd numbers from 1 to 100

  perl -le '@odd = grep {$_ % 2 == 1} 1..100; print "@odd"'

5.11 Generate an array with even numbers from 1 to 100

      perl -le '@even = grep {$_ % 2 == 0} 1..100; print "@even"'

5.12 Find the length of a string

    perl -le 'print length "one-liners are great"'

5.13 Find the number of elements in an array

    perl -le '@array = ("a".."z"); print scalar @array'

最后编辑于：2018.09.21 23:04:20