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Cookbook: Job control extension
Import module 'jobctrl' to launch and interact with background processes by prepending system commands with '&', or to kill foreground tasks that are preventing you from continuing with your work and are just too stubborn to die with the usual ctrl+C.
Launch IPython instance, run a blocking command:
[Q:/ipython]|1> import jobctrl [Q:/ipython]|2> cat
Observe that it starts blocking.
Now launch a new IPython prompt and kill the 'cat' process:
IPython 0.8.3.svn.r2919 [on Py 2.5] [Q:/ipython]|1> import jobctrl [Q:/ipython]|2> %tasks 6020: 'cat ' (Q:\ipython) [Q:/ipython]|3> %kill SUCCESS: The process with PID 6020 has been terminated. [Q:/ipython]|4>
(you don't need to specify PID for %kill if only one task is running)
Note that only the processes that are launched when 'jobctrl' is enabled are affected.
See the example below. "IPython job" object is just a very thin wrapper over subprocess.Popen object, with an added __repr__ and "go" method.
[ipython]|1> import jobctrl
[ipython]|2> &ls C*
<2> <IPython job "ls C*">
[ipython]|3> &ls e*
<3> <IPython job "ls e*">
[ipython]|4> &ls e*
<4> <IPython job "ls e*">
[ipython]|5> &ls RE*
<5> <IPython job "ls RE*">
[ipython]|7> _2.go
-----------> _2.go()
ChangeLog
[ipython]|8> _3.go
-----------> _3.go()
eggsetup.py
[ipython]|9> _5.go
-----------> _5.go()
README
README_Windows.txt
[ipython]|10> _4.go
------------> _4.go()
eggsetup.py
Note how "jobs" are just objects in the output history. You can use all the subprocess.Popen methods on the object, but this example just uses "go".
See http://docs.python.org/library/subprocess.html#popen-objects
Here's another example: I want to make a macro radio_trance that launches VLC on a net radio stream. I have the "vlc" alias that points to the actual binary of vlc, so I launch it via the alias:
[ipython]|1> import jobctrl [ipython]|2> vlc http://di.fm/mp3/trance.pls
But this blocks the ipython window, while I want to listen to it on the background!
I check out the command history to get the expanded version of the command:
[ipython]|3> hist
1: import jobctrl
2: _ip.system("q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls")
3: _ip.magic("hist ")
I copy-paste the command string from line #2 (and add '&' to make it a background process:
[ipython]|4> &q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls
<4> <IPython job "q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls">
(''' Note that this is unnecessarily hard'''. In fact, with the new recursive alias expansion, you can do this simply with aliases without having to resort to manual copy-paste)
So far so good, I can hear the music playing in the background! Now I'll make a macro that both imports jobctrl and launches vlc (lines 1 and 4), and %store it:
[ipython]|5> hist
1: import jobctrl
2: _ip.system("q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls")
3: _ip.magic("hist ")
4: _ip.startjob("q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls")
5: _ip.magic("hist ")
[ipython]|6> macro radio_trance 1 4
Macro `radio_trance` created. To execute, type its name (without quotes).
Macro contents:
import jobctrl
_ip.startjob("q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls")
[ipython]|7> store radio_trance
Stored 'radio_trance' (Macro)
Now I restart ipython and try the macro:
Q:\ipython>python IPython.py -p sh
Py 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] IPy 0.7.3.svn
[ipython]|1> radio_trance
<1> Executing Macro...
<3> <IPython job "q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls">
[ipython]|4> hist
1: radio_trance
2: import jobctrl
3: _ip.startjob("q:/opt/VLC/vlc.exe http://di.fm/mp3/trance.pls")
4: _ip.magic("hist ")
And verify that it works.
[ipython]|1> &rad_trance
<1> <IPython job "q:/opt/VLC/vlc.exe http://di.fm/mp3/harddance.pls " PID=196>
[ipython]|2> # this music is boring me.... I want it to stop right now!
[ipython]|3> _1.kill
-----------> _1.kill()
SUCCESS: The process with PID 196 has been terminated.
See the source of jobctrl.py