I tend to write shell scripts in Ruby even more often than bash. I'm proficient in both, but I find that the larger the script, the more I'm affected by the lack of language support in bash, and the many oddities such as the many problems with quoting and string splitting and the hacks/special mechanisms needed to work around them.
Even though bash has some "modern" features, they're typically a bit weird and hard to remember: bash has arrays, for example, but the syntax is bizarre; you can write functions, but you can't declare the parameters, only access them as $1, $2, etc.; and so on. Occasionally I have to look up some expression syntax (like which bracket syntax to use for arithmetics, or whether "if" should have one or two brackets, and whether it's [[ a && b ]] or [[ a ]] && [[ b ]]) just because it's so damn different. It's painfully obvious that bash wasn't planned; so much of its evolution can be felt in the layers of hacks.
And with Ruby it's much easier to refactor to do things like logging (eg., when spawning a sub-command, only show its output if it fails), or provide cleanup (express your script with the command pattern, with commands that know how to commit and undo themselves), or use existing libraries.
Ruby's syntax — the ability to omit parantheses, the support for running shell commands with backticks — makes it particularly suited. For example:
if [ -e ./somefile ]; then
./somecommand ./somefile
(cd ./somedir && make)
installdir=`getsomeconfig`
cp build/mybinary $installdir/bin
fi
In Ruby:
if File.exist? "somefile"
`./somecommand ./somefile`
Dir.chdir 'somedir' do
`make`
end
installdir = `getsomeconfig`
cp "build/mybinary", "#{installdir}/bin"
end
The last line requires that you initially do:
require 'fileutils'; include FileUtils
Now you have a bunch of utilities (cd, cp, mv, mkdir, mkdir_p, etc.) as global Ruby methods.
Bash sucks when it comes to arrays. Last week I had to change the 'input field separator' because bash arrays are kinda-sorta-but-not-really space delimited, which causes problems where elements have whitespace. I then had to revert the IFS immediately after the required operation, as that screwed something else up later in the script.
I like bash scripting, but the moment to use another language for a script for me is "will this require an array?"
Even though bash has some "modern" features, they're typically a bit weird and hard to remember: bash has arrays, for example, but the syntax is bizarre; you can write functions, but you can't declare the parameters, only access them as $1, $2, etc.; and so on. Occasionally I have to look up some expression syntax (like which bracket syntax to use for arithmetics, or whether "if" should have one or two brackets, and whether it's [[ a && b ]] or [[ a ]] && [[ b ]]) just because it's so damn different. It's painfully obvious that bash wasn't planned; so much of its evolution can be felt in the layers of hacks.
And with Ruby it's much easier to refactor to do things like logging (eg., when spawning a sub-command, only show its output if it fails), or provide cleanup (express your script with the command pattern, with commands that know how to commit and undo themselves), or use existing libraries.
Ruby's syntax — the ability to omit parantheses, the support for running shell commands with backticks — makes it particularly suited. For example:
In Ruby: The last line requires that you initially do: Now you have a bunch of utilities (cd, cp, mv, mkdir, mkdir_p, etc.) as global Ruby methods.