- file_io2: replace the manual line_number counter with
.lines().enumerate(), and replace
buffered_file_writer.write(format!(...).as_bytes()) with writeln!,
which both formats and guarantees a complete write (write_fmt loops
internally, unlike a single Write::write call).
- file_io3: replace the manual match on file_path.parent() with
.ok_or_else(...)? for a more idiomatic Option-to-Result conversion.
Verified locally: both solutions compile under edition 2024, clippy is
silent, and running them still produces identical output (3 lines
processed / 117-byte file, non-readonly permissions) with no leftover
files.
- file_io3: replace the hardcoded expected file size (117) with
SAMPLE_TEXT.len(), so the check is derived from the actual content
instead of an unexplained magic number.
- file_io3: use create_dir_all instead of create_dir, and add a
sample_file_path() helper shared by main/create_required_files/
file_cleanup to avoid three separate ad-hoc path constructions.
- file_io1/file_io2: hoist the sample text into a SAMPLE_TEXT constant
used by both the exercise and its solution, removing duplicated
literals.
No behavioral change: all three solutions were rebuilt and run
locally, producing identical output (file size still 117, permissions
still non-readonly) with no leftover files.
Adds three new exercises under exercises/24_file_io/, as proposed in rust-lang/rustlings#2233:
- file_io1: read a whole file with fs::read_to_string and handle the Result.
- file_io2: read/write a file efficiently with BufReader/BufWriter.
- file_io3: build a path with PathBuf and inspect it with .metadata().
Includes matching solutions and a README describing the learning goal of
each exercise.
