Hello, Core lib developers :)
Java is pretty decent for shell scripts style programs now days!
I'd like to suggest a couple of additions to the standard library to
make it better.
## Background
By "shell script style programs" I mean programs that don't have a GUI
and mostly perform these tasks: Move files around, read and write files,
executes commands, execute external programs and fetch network files.
Simple shell scripts are often written in Bash or Batch. Slightly more
complex scripts are often written in for example Python.
For an organisation that works mostly with Java it's an advantage to be
able to instead use Java for these slightly complex scripts, so that
developers can use their existing Java skills instead of learning an
alternative language.
Historically Java has been a rather poor choice for shell scripts,
because of need for a separate compile step, and the verbosity of the
language and the relevant libraries.
Now days Java is have become reasonable choice, after the following
additions:
* New file API based on Path and Files in Java 7.
* Addition and improvement of ProcessBuilder in Java 5-9.
* Addition of java.net.http.HttpClient in Java 11.
* Ability to run single file programs without a separate compilation
step in Java 11.
* Features to write more succinct code, such as collections factories
and records.
However: A few common tasks are still hard or unnecessary fiddly. Many
of these tasks can be performed with external libraries such as Guava or
Apache Commons, but for shell script style programs it's hard to include
external libraries.
I think this could be helped by a few relatively minor additions to the
standard library.
## Tasks that would benefit from improvements
Ordered approximately according to how important I think they are.
### 1. Wait for termination of an external process and get its output
* Wait for the termination of an external process, with a timeout, and
then capturing its output as a string.
* The best current solution I have been able find is to use a Future to
wait for the output.
* Example solution:
https://stackoverflow.com/questions/41491327/how-to-get-the-output-from-a-process-and-set-a-timeout/73486466#73486466
* This can probably be fixed by some addition to ProcessBuilder.
### 2. Recursively delete a directory
* Recursively delete a directory, including its files and nested
directories.
* The best current solution I have been able find:
https://www.baeldung.com/java-delete-directory
### 3. Pack and unpack a zip file
* Create a zip file with the arbitrary contents of a directory,
including nested directories.
* Unpack a full zip file including all files and nested sub-directories,
then write it to disk.
* The best current solution I have been able find involves manually
looping over all files or zip entries:
https://www.baeldung.com/java-compress-and-uncompress#unzip
* This can often a done by calling an external command, but a pure Java
solution would be better.
### 4. Report download process in HttpClient
* Some way to report how much of a large file that has been downloaded
using HttpClient.
* A very minor improvement.
* The best current solution I have been able find involves creating a
custom BodyHandler: https://stackoverflow.com/a/77250200/452775
### 5. List directory contents eagerly
* Currently there is `Files#list`, but the returned steam needs to be
closed using a try-with-resources.
* This is minor but re-occurring annoyance. An eager version of this
method would be a quality-of-life improvement.
* Guava has `MoreFiles#listFiles` for this.
### 6. Parse and generate JSON
* This is currently explored as JEP 198: https://openjdk.org/jeps/198
* I think a very simple solution would be sufficient for shell script
style programs.
## Conclusion
I think a few small additions to the standard library could solve these
problems and be useful both to shell script style programs as well as
other Java programs.
Best Regargs,
Jens Lideström, Java and MUMPS developer
