File & process IO

Read and write files, run subprocesses — real in Raku++, but there's no browser filesystem.

Raku++ can read and write files and launch subprocesses, exactly as Rakudo does. The browser playground has no filesystem and can't spawn processes, so these examples are shown with their verified output (from the interpreter and --exe) rather than a Run button.

Running a subprocess #

run launches an external command; with :out you capture its standard output.

my $r = run "echo", "from a subprocess", :out;
say $r.out.slurp(:close).chomp;

from a subprocess

Writing and reading a file #

spurt writes a whole string to a path; slurp (or .lines) reads it back. Here a temp file is written, its lines counted and indexed, then removed.

my $f = $*TMPDIR.add("spec-io-demo.txt");
spurt $f, "alpha\nbeta\ngamma\n";
say $f.lines.elems;
say $f.lines[1];
$f.unlink;

3
beta

Notes #

• File handling: spurt/slurp for whole files, open for a handle, .lines/.words to iterate, IO::Path methods (.e, .d, .add, .unlink) for paths.
• run/shell start subprocesses; :out/:err capture their streams.
• $*TMPDIR, $*CWD, $*HOME are IO::Path handles to standard locations.
• None of this exists in the browser sandbox — run such programs with the interpreter (rakupp program.raku) or a compiled binary (rakupp --exe program.raku).