Declare a shell alias in a ruby file

Ruby
1

Hello,

I’m trying to declare a shell alias from a ruby file.

here is the file test.rb :

begin test.rb

alias world='echo hello'

end test.rb

I’m launching it :

ruby test.rb

Then launching the alias :

world
-bash: world: command not found

Does anyone know how do i declare a shell alias from a ruby file ?

2

At 2009-09-03 11:22AM, “jney” wrote:

Hello,

I’m trying to declare a shell alias from a ruby file.

here is the file test.rb :

begin test.rb

alias world='echo hello'

you spawn a shell, declare the alias, then the shell exits taking the
alias with it.

I’m launching it :

ruby test.rb

Then launching the alias :

world
-bash: world: command not found

Does anyone know how do i declare a shell alias from a ruby file ?

If you want a child process to make changes to the current process, you
have to make the child tell the parent what to do and then the parent
has to do it.

alias.rb outputs shell commands

puts <<END
alias world=‘echo hello’
END

shell evaluates the output of the ruby program

eval $(ruby alias.rb)
world

3

Jean-sébastien Jney wrote:

Hello,

I’m trying to declare a shell alias from a ruby file.

here is the file test.rb :

begin test.rb

alias world='echo hello'

end test.rb

I’m launching it :

ruby test.rb

Then launching the alias :

world
-bash: world: command not found

Does anyone know how do i declare a shell alias from a ruby file ?

You cannot.

The processes are started as follows:

your shell --------------> ruby process --------> another shell
ruby test.rb xxx

Each process is completely independent of the others - with its own
address space, and its own copy of the ENVironment. When the second
shell terminates, it cannot affect the ruby process, nor the original
shell which started that ruby process.

The only way you can do this is from the original shell itself. Either
type your alias command at the shell prompt, or put it in a file and do

. myscript

The dot (.) means “read this file and execute it as commands within this
shell”

You may find the comp.unix.shell FAQ helpful.

4

At 2009-09-04 04:32AM, “Jean-Sébastien” wrote:

ruby one, althrough my file is starting by “#!/usr/bin/env ruby”.
Brian is saying that the ruby script writes shell commands to a file
named “myscript” (instead of printing them to stdout). Then the shell
will source that file (instead of ‘eval’-ing its stdin).

5

On 3 sep, 18:16, Brian C. [email protected] wrote:

I’m launching it :
The processes are started as follows:
type your alias command at the shell prompt, or put it in a file and do

. myscript

The dot (.) means “read this file and execute it as commands within this
shell”

You may find the comp.unix.shell FAQ helpful.

Posted viahttp://www.ruby-forum.com/.

Thank you both of you.

eval $(ruby test.rb) works for me.
But output have to a one line command separate by “;”.

“. myscript” doesn’t not work for me. It doesn’t read my file as a
ruby one, althrough my file is starting by “#!/usr/bin/env ruby”.

Thanks.

6

Glenn,

Do you know how to unsubscribe from these e-mails?

Thanks,
Steve

— On Fri, 9/4/09, Glenn J. [email protected] wrote:

From: Glenn J. [email protected]
Subject: Re: declare a shell alias in a ruby file
To: “ruby-talk ML” [email protected]
Date: Friday, September 4, 2009, 6:30 AM

At 2009-09-04 04:32AM, “Jean-Sébastien” wrote:

 ruby one, althrough my file is starting by “#!/usr/bin/env ruby”.
Brian is saying that the ruby script writes shell commands to a file
named “myscript” (instead of printing them to stdout). Then the shell
will source that file (instead of ‘eval’-ing its stdin).