Raku Books / Raku One-Liners / Command-Line Options

Reading files with $*ARGFILES

$*ARGFILES is a built-in dynamic variable that may be handy when working with multiple input files.

How do you read two or more files passed in the command line?

$ raku work.pl a.txt b.txt

If you need to process all files together as if they are a single data source, you could ask the variable to do the job in a one-liner:

.say for $*ARGFILES.lines

Inside the program, you don’t have to think about looping over the files; $*ARGFILES will automatically do that for you.

If there are no files in the command line, the variable will be attached to STDIN:

$ cat a.txt b.txt | raku work.pl

Handy indeed, isn’t it?

$*ARGFILES and MAIN

I also have to warn you if you will want to use the $*ARGFILES variable in bigger programs. Consider the following example:

sub MAIN(*@files) {
    .say for $*ARGFILES.lines;
}

In the recent versions of Raku, $*ARGFILES works differently inside the MAIN subroutine and outside of it.

This program will perfectly work with the earlier versions (before and including Rakudo version 2018.10). Starting from Rakudo Star 2018.12, $*ARGFILES, if used inside MAIN, is always connected to $*IN.

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