When comparing Bash (Bourne-Again SHell) vs Xtend, the Slant community recommends Bash (Bourne-Again SHell) for most people. In the question“What is the best programming language to learn first?” Bash (Bourne-Again SHell) is ranked 34th while Xtend is ranked 68th. The most important reason people chose Bash (Bourne-Again SHell) is:
Bash is the default shell on virtually every UNIX system. Making it very portable across different systems and once you get used to it, you can use it everywhere.
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Pros
Pro Default shell on most systems
Bash is the default shell on virtually every UNIX system. Making it very portable across different systems and once you get used to it, you can use it everywhere.
Pro Plenty of examples and tutorials
Since this is very mature shell there is a lot of great examples and other resources describing how to do almost everything.
Pro Rich scripting capabilities on a single line
Want to run something 5 times? Write a throw-away loop: for i in 1 2 3 4 5; do date; done
If you need it 100 times? Not a problem: for i in {1..100}; do date; done
or: for ((i=0; i<100; ++i)); do date; done
How about emailing yourself when remote server is back online? Sure thing: while ! ping -c1 example.com &>/dev/null; do date; sleep 5; done && mailx -s 'server is back!' me@myself.com
Pro POSIX compatible
Pro Emacs-like keyboard control
By default, BASH uses shortcuts and concepts very similar to Emacs, so learning one often results in familiarity with the other.
Pro Rich built-in features
By default, there are many built-in features. They make really complex and reliable programs possible. In comparison to dash, for example, you can do the same tasks in less time and fewer lines of code.
Pro Variables and aliases are listed the way they are built
alias
and set
will list aliases and variables in a format that can be run directly with no modifications. Even if the values contain \n.
This is handy if you want to modify a value.
Pro Recursive globbing
ls **/*.log
for example is supported by Bash if you set shopt -s globstar
.
Pro Man page is a trove of wonders
While the manual "page" is nearly a hundred pages long, it is actually surprisingly succinct and stuffed with good information. It is often better than Googling for answers when writing shell scripts. The way it is written makes it easy to stumble upon useful new programming features just by flipping through it .
NOTE: If you find it dense and hard to read at the command line, look for the PDF version.
Pro vi mode is more comprehensive than on other shells
Vi editing mode works without a glitch. "_" will print you the last argument of the latest command (zsh won't). VI mode is fast off the bat - You don't have to reset any variable (like "KEYTIMEOUT" in zsh) for that.
Pro Copyright license is GPL 3+
Bash is licensed under the GNU General Public License ≥3, which gives much stronger assurances that the right to use it can't be restricted.
For example, Microsoft would not be able to claim in court that, even though they've distributed Bash with the GPLv3, a license that explicitly grants people freedom, now Bash is essentially proprietary due to software patents and everyone who uses Bash owes them money. (This may sound ludicrous to those who were not alive when Microsoft tried a similar scheme against Linux fifteen years ago).
The GPLv3 is a license that reflects the genuine ethical issues that arise when people give their time and skills to collaboratively build software. While most people wouldn't insist that their UNIX shell is licensed under the GPLv3+, it does matter and is a big PRO for Bash.
Pro Built-in 'help'... helps a lot
Built-in 'help' provides quick and efficient help on builtins and keywords.
Pro Rich scripting capabilities
BASH scripting is a rich and robust language.
Pro Ruby-like syntactic conveniences
Lambdas are written like Smalltalk's blocks. If it's the last argument, it can go after the parentheses like Ruby's blocks. Parentheses on method calls are optional.
Pro Type inference
It uses Java's static type system, but you don't have to declare the type of everything all the time, since the Xtend compiler can usually figure it out. This also dramatically cuts down on Java's infamous verbosity.
Pro Code runs just as fast as Java
Because Xtend relies heavily on JDK and Android classes, it runs just as fast as native Java code.
Pro Easy to switch back to Java
Xtend is a low-risk option. Because it compiles to human-readable Java, if you decide you don't like it for your project, you can just switch back to Java without losing your work.
Pro Extend even library classes with new methods
This is where it gets its name. You can open classes and add new methods, kind of like Ruby. (Of course this has to be compiled to Java, so really it lives in a kind of helper class.)
Pro Succint
Uses functional features ,which are very concise and idiomatic. Plus it has annotations, which cuts down on the Java boilerplate.
Pro Better defaults than Java
Methods are public if you don't specify, and fields are private. Locals declared with val
in Xtend are final
in Java. This dramatically cuts down on Java's infamous verbosity.
Cons
Con Extremely complicated and inconsistent rules
In Bash, exceptions are the rule, not even all being described by the main page.
There are a grand total of 5 different ways of quoting, sometimes even when one does not want to, for instance in command substitutions. These are all based around preserving the literal meaning of every character, with an exception list. There is even an exception list to the exception list in 4 of the 5, regarding how the backslash behaves! The behavior of the backslash is also one of the quoting rules, so naturally, it also has an exception in how it works when it stands before a newline as compared to other characters.
Bash has several layers of interpretations, all to be kept in mind:
The ~ expands to the home of the current user. So if you store it in a variable, can you use it that way? Nope: tilde expansion comes before variable expansion.
Aha, so that's how it works! Then, since applying quotation happens after redirections are set up, it must mean that redirecting within quotes works, right? Nope: there is an exception! If a redirection symbol is not quoted, quotation around the symbol is observed, but is not removed. So, since variable expansion also comes after setting up redirections, and no exceptions are described here in the man page, getting the name of a file from a variable and using it as a target should not work, right? No: redirection does not actually take place when the symbols are being read, the symbols are merely removed and are noted for later, right before when the actual command runs.
Apart from 5 types of quotation, there are basically 2 quoting phases, 2 word splitting phases (with only one being controllable), and a tokenization phase on top of that.
If you have a command, it could be an alias, a special built in, a non-special built in, a symbolic link to a file, a regular file, a function, with different rules regarding how they can be overridden, if redirection happens before or after arguments have been passed (what does "time my_command 2>&1 >log_file" do?), etc.
This list is admittedly long, but it doesn't even scratch the surface of the bloat, complexity and inconsistencies of Bash.
Con GPL3 is not compatible with Apple's lawyers
Apple, one of the largest distributors of UNIX systems, only ships an ancient version of bash that predates the iPhone.
No one knows why as Apple hasn't said, but the version Apple includes in MacOS is from right before the license was updated to version 3 of the GNU GPL (General Public License). Other major companies (IBM, Microsoft) have had no problem shipping the latest version of bash
, so it's unclear what Apple's lawyers are averse to. The GPL has always said that if you distributed a program, you granted everyone the right to use it freely. The biggest change in version 3 was the addition, "...and that includes software patents."
This was necessary because back in 2006 Microsoft was demanding that any company that uses Linux pay them or get sued for infringing on their patents. They even took some companies, like TomTom, to court. No software which can be restricted retroactively like that is truly free, so GPL 3+ includes a clause saying that if you distribute the program, then you are also granting license to any patents you own that are necessary to run it.
What patents Apple has that bash could possibly infringe on is a mystery, but the bigger question is, Why does Apple even care? So what if they are granting people the right to run bash without being sued by Apple. It's not like they were planning on doing that, right?
Even though it is not bash's fault that it is not Apple Lawyer-approved, this is a CON for it because a lot of people use Apple products. While there are methods like brew
to install a current version of bash, Apple does not make it obvious to their customers what they are missing.
Con Compatibility can be a curse
One of bash's claims to fame is compatibility with previous versions of itself and historic shells. But, doing that means that new features are often written in tortured, awkward syntax that is not easy to learn. For example, bash uses the POSIX way of doing arithmetic: to add 5+3 you must put the numbers in double parentheses with a dollar sign at the start: x=$((5+3)). It is true that many shells suffer from this same CON, but since bash is such an important shell, it has less wiggleroom to ditch clunky ideas that might break existing scripts.
Con Lags behind on features compared to ZSH and Fish
People who wants power features or to customize their shell experience use zsh or fish.
Con Filename expansion is not consistent
filename expansion is not consistent. "echo *" will print the names of the files in your current dir, if there are any... and will print "*" if there are none.
Con Non-intuitive shell expansion in for loops
If there are no .sh files, this will print mask itself:
for filename in *.sh; do
echo $filename
done
Con No out-of-the-box command autocompletion
To have command autocompletion in bash you need to install third-party plug-ins.
Con One of the most dangerous languages around
What it is mostly used for are file system operations. Guess what it is bad at? Operating on files. It automatically splits and carries out filename expansion on every single string resulting from variable expansion and command substitution unless quoted, by default on whitespace, whilst spaces are very common in filenames.
Before that, it even does pathname expansion, so woe to anywone who does not want to actually operate on files, but has a globbing metacharacter stored anywhere in a variable.
This means what you store in a variable is not going to be what will ACTUALLY be accessed.
If an empty variable is unquoted, it disappears completely due to word splitting, sometimes leading to applications signalling a missing parameter at a wrong position.
If quoted however, said variables cannot be iterated over in a loop, no matter what character one uses for word splitting.
If you use any globbing pattern with a command, be sure to use -- after the option arguments or if none are present, before starting the pattern with a mandatory ./
Otherwise, another Bash script run gone wrong or a hacker can create files named like an option ("-f", for instance) and your program will happily accept it as such, if it results from globbing.
For interactive use, it is convenient. For programming, it is a no-go.
Con Difficult to configure in Android Studio
Con Slower compilation
Unlike most JVM languages, Xtend compiles to Java rather than directly to JVM bytecode. So you have to compile everything four times for Android: from Xtend to Java, from Java to JVM bytecode (.class files), from .class to .dex bytecode, and then AOT compilation from .dex to native ARM upon installation. This can really slow down development and testing vs a more interactive language like Clojure.