This explanation is based on a commented Ruby script from a friend of mine. If you want to improve the script, feel free to update it at the link.
First, note that when Ruby calls out to a shell, it typically calls /bin/sh
, not Bash. Some Bash syntax is not supported by /bin/sh
on all systems.
Here are ways to execute a shell script:
cmd = "echo 'hi'" # Sample string that can be used
Kernel#`
, commonly called backticks – `cmd`
This is like many other languages, including Bash, PHP, and Perl.
Returns the result (i.e. standard output) of the shell command.
Docs: http://ruby-doc.org/core/Kernel.html#method-i-60
value = `echo 'hi'`
value = `#{cmd}`
Built-in syntax, %x( cmd )
Following the x
character is a delimiter, which can be any character.
If the delimiter is one of the characters (
, [
, {
, or <
,
the literal consists of the characters up to the matching closing delimiter,
taking account of nested delimiter pairs. For all other delimiters, the
literal comprises the characters up to the next occurrence of the
delimiter character. String interpolation #{ ... }
is allowed.
Returns the result (i.e. standard output) of the shell command, just like the backticks.
Docs: https://docs.ruby-lang.org/en/master/syntax/literals_rdoc.html#label-Percent+Strings
value = %x( echo 'hi' )
value = %x[ #{cmd} ]
Kernel#system
Executes the given command in a subshell.
Returns true
if the command was found and run successfully, false
otherwise.
Docs: http://ruby-doc.org/core/Kernel.html#method-i-system
wasGood = system( "echo 'hi'" )
wasGood = system( cmd )
Kernel#exec
Replaces the current process by running the given external command.
Returns none, the current process is replaced and never continues.
Docs: http://ruby-doc.org/core/Kernel.html#method-i-exec
exec( "echo 'hi'" )
exec( cmd ) # Note: this will never be reached because of the line above
Here's some extra advice:
$?
, which is the same as $CHILD_STATUS
, accesses the status of the last system executed command if you use the backticks, system()
or %x{}
.
You can then access the exitstatus
and pid
properties:
$?.exitstatus
For more reading see:
You can specify formal arguments in rake by adding symbol arguments to the task call. For example:
require 'rake'
task :my_task, [:arg1, :arg2] do |t, args|
puts "Args were: #{args} of class #{args.class}"
puts "arg1 was: '#{args[:arg1]}' of class #{args[:arg1].class}"
puts "arg2 was: '#{args[:arg2]}' of class #{args[:arg2].class}"
end
task :invoke_my_task do
Rake.application.invoke_task("my_task[1, 2]")
end
# or if you prefer this syntax...
task :invoke_my_task_2 do
Rake::Task[:my_task].invoke(3, 4)
end
# a task with prerequisites passes its
# arguments to it prerequisites
task :with_prerequisite, [:arg1, :arg2] => :my_task #<- name of prerequisite task
# to specify default values,
# we take advantage of args being a Rake::TaskArguments object
task :with_defaults, :arg1, :arg2 do |t, args|
args.with_defaults(:arg1 => :default_1, :arg2 => :default_2)
puts "Args with defaults were: #{args}"
end
Then, from the command line:
> rake my_task[1,false]
Args were: {:arg1=>"1", :arg2=>"false"} of class Rake::TaskArguments
arg1 was: '1' of class String
arg2 was: 'false' of class String
> rake "my_task[1, 2]"
Args were: {:arg1=>"1", :arg2=>"2"}
> rake invoke_my_task
Args were: {:arg1=>"1", :arg2=>"2"}
> rake invoke_my_task_2
Args were: {:arg1=>3, :arg2=>4}
> rake with_prerequisite[5,6]
Args were: {:arg1=>"5", :arg2=>"6"}
> rake with_defaults
Args with defaults were: {:arg1=>:default_1, :arg2=>:default_2}
> rake with_defaults['x','y']
Args with defaults were: {:arg1=>"x", :arg2=>"y"}
As demonstrated in the second example, if you want to use spaces, the quotes around the target name are necessary to keep the shell from splitting up the arguments at the space.
Looking at the code in rake.rb, it appears that rake does not parse task strings to extract arguments for prerequisites, so you can't do task :t1 => "dep[1,2]"
. The only way to specify different arguments for a prerequisite would be to invoke it explicitly within the dependent task action, as in :invoke_my_task
and :invoke_my_task_2
.
Note that some shells (like zsh) require you to escape the brackets: rake my_task\['arg1'\]
Best Answer
I've found the way to get this working!
Basically, I was doing everything right apart from doing the 'post' call in the right place.
The post call have to be done after the:
i.e. the code below will work without any problems:
and not before.
I hope will help someone! ;)
D.