Programming Forums > Script Programming > Ruby

Jessehk · Apr 8th, 2007, 12:37 AM

I have a stupid question.
I know in Ruby you can get the output of a command by encasing itin backquotes.

For example:

$ irb
irb(main):001:0> output = `uname -r`
=> "2.6.20-ARCH\n"

Now, my question. Say I have a program like apt-get (pacman in this case).
What I want to do is start the program from inside a Ruby script and see the output as it's running.

I think this is possible, because I've seen it done in other scripts (though not necessarily Ruby). Any ideas?

glimmy · Apr 8th, 2007, 1:19 AM

You could try using IO :: popen:

(Toggle Plain Text)

$ irb
irb(main):001:0> io = IO::popen('echo 1 && sleep 10 && echo 2')
=> #<IO:0x4028c0fc>
irb(main):002:0> while io
irb(main):003:1> print io.readline
irb(main):004:1> end
1
2
EOFError: end of file reached
        from (irb):3:in `readline'
        from (irb):3
        from :0

Of course you would have to filter out the exception it gets when it reaches EOF

(It's hard to tell by just reading this but there is a delay between when it prints 1 and 2 when I did it)

Apr 8th, 2007, 12:37 AM	#1
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 640 Rep Power: 4	Start another program from Ruby and view ouput? I have a stupid question. I know in Ruby you can get the output of a command by encasing itin backquotes. For example: (Toggle Plain Text) $ irb irb(main):001:0> output = `uname -r` => "2.6.20-ARCH\n" $ irb irb(main):001:0> output = `uname -r` => "2.6.20-ARCH\n" Now, my question. Say I have a program like apt-get (pacman in this case). What I want to do is start the program from inside a Ruby script and see the output as it's running. I think this is possible, because I've seen it done in other scripts (though not necessarily Ruby). Any ideas? __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

Apr 8th, 2007, 1:19 AM	#2
glimmy Programmer Join Date: May 2005 Location: Minnesota Posts: 42 Rep Power: 0	You could try using IO :: popen: (Toggle Plain Text) $ irb irb(main):001:0> io = IO::popen('echo 1 && sleep 10 && echo 2') => #<IO:0x4028c0fc> irb(main):002:0> while io irb(main):003:1> print io.readline irb(main):004:1> end 1 2 EOFError: end of file reached from (irb):3:in `readline' from (irb):3 from :0 $ irb irb(main):001:0> io = IO::popen('echo 1 && sleep 10 && echo 2') => #<IO:0x4028c0fc> irb(main):002:0> while io irb(main):003:1> print io.readline irb(main):004:1> end 1 2 EOFError: end of file reached from (irb):3:in `readline' from (irb):3 from :0 Of course you would have to filter out the exception it gets when it reaches EOF (It's hard to tell by just reading this but there is a delay between when it prints 1 and 2 when I did it)

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Programming Forums > Script Programming > Ruby

Start another program from Ruby and view ouput?