Examples of short one-lines

To warm up, let’s start with a few simple one-liners for working with files. (There’s also the whole Chapter 2 which is about working with files).

Double-space a file

$ raku -npe's/$/\n/' text.txt

Remove all blank lines

$ raku -ne'.say if .chars' text.txt

Depending on how you define ‘blank’, you may want another one-liner that skips the lines containing whitespaces:

$ raku -ne'.say if /\S/' text.txt

Number all lines in a file

$ raku -ne'say ++$ ~ ". " ~ $_' text.txt

This code, probably, requires a comment. The $ variable is a state variable and it can be used without declaration.

Convert all text to uppercase

$ raku -npe'.=uc' text.txt

Strip whitespace from the beginning and end of each line

$ raku -npe'.=trim' text.txt

Print the first line of a file

$ raku -ne'.say ; exit' text.txt

Print the first 10 lines of a file

$ raku -npe'exit if $++ == 10' text.txt

This time, the postfix ++ operator was applied to the $ variable.

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