How to install updates from console on linux

There are two options to install updates.

1. Using yum
2. GUI

It is very simple if you have already yum installed on your machine.

$ yum update

It should automatically install all the updates of different software on your machine. 

Using GUI, it is very simple process. Just follow the instructions on GUI.

Problem with tagger and chunkers of NLTK on linux

I installed NLTK using the commands which were found here: http://nltk.org/install.html

Everything got installed successfully. So when I started using this nltk package like this:

python
>>> import nltk
>>> text = nltk.word_tokenize("And now for something completely different")
>>> text
['And', 'now', 'for', 'something', 'completely', 'different']

But when I try to tag these tokens, there are some errors as shown below.

>>>  nltk.pos_tag(text)
  File "", line 1
    nltk.pos_tag(text)
    ^
IndentationError: unexpected indent
>>> nltk.pos_tag(text)
Traceback (most recent call last):
  File "", line 1, in
  File "/usr/lib/python2.6/site-packages/nltk/tag/__init__.py", line 99, in pos_tag
    tagger = load(_POS_TAGGER)
  File "/usr/lib/python2.6/site-packages/nltk/data.py", line 605, in load
    resource_val = pickle.load(_open(resource_url))
  File "/usr/lib/python2.6/site-packages/nltk/data.py", line 686, in _open
    return find(path).open()
  File "/usr/lib/python2.6/site-packages/nltk/data.py", line 467, in find
    raise LookupError(resource_not_found)
LookupError:
**********************************************************************
  Resource 'taggers/maxent_treebank_pos_tagger/english.pickle' not
  found.  Please use the NLTK Downloader to obtain the resource:
  >>> nltk.download()
  Searched in:
    - '/root/nltk_data'
    - '/usr/share/nltk_data'
    - '/usr/local/share/nltk_data'
    - '/usr/lib/nltk_data'
    - '/usr/local/lib/nltk_data'
**********************************************************************

The way you can fix it is: Run this command which downloads the tagger:
>>> nltk.download('maxent_treebank_pos_tagger')

It downloads this package to some directory on your machine. For me it downloaded here: /root/nltk_data...

And all the system related files with regard to NLTK are in this directory: /usr/lib/python2.6/site-packages/nltk
So, I created a new directory called 'taggers' and copy this 'maxent_treebank_pos_tagger' to this new directory named: /usr/lib/python2.6//site-packages/nltk/taggers/

Now when you run this command:
>>> tagged = nltk.pos_tag(tokens)
[('At', 'IN'), ('eight', 'CD'), ("o'clock", 'JJ'), ('on', 'IN'), ('Thursday', 'NNP'), ('morning', 'NN')]

Similarly when you try to do this:
>>> entities = nltk.chunk.ne_chunk(tagged)
You will see similar results that you have to download chunker and corpora, follow the similar procedure and execute these two commands:

>>> nltk.download('maxent_ne_chunker')
>>> nltk.download('words')

This can help you install the chunkers package and when you execute this command, you can get the parse tree
>>> entities = nltk.chunk.ne_chunk(tagged)
>>> entities
Tree('S', [('At', 'IN'), ('eight', 'CD'), ("o'clock", 'JJ'), ('on', 'IN'), ('Thursday', 'NNP'), ('morning', 'NN'), Tree('PERSON', [('Arthur', 'NNP')]), ('did', 'VBD'), ("n't", 'RB'), ('feel', 'VB'), ('very', 'RB'), ('good', 'JJ'), ('.', '.')])

Hope this helps!

Install/add network printer to your system list in linux through command line

Initially check if CUPS (Common Unix Printing System) daemon is running or not using this command:

$$ /etc/init.d/cups status

You will see something like this on your terminal:

$$ cupsd (pid ****) is running...

If the daemon is not running, then start the daemon using these commands:

$$ /etc/init.d/cups start
$$ chkconfig cups on

To add the network printer, use this command:

$$ lpadmin -p Printer_name -E -v socket://


To set a default printer:

$$ lpadmin -d  Printer_name

To check the printer status and see if printer is in ready mode:

$$ lpq

 You see something like this when your printer is ready and there are no entries:

$$ Printer_name  is ready
$$ no entries

To check the printers installed on your machine, you can use this command:

$$ lpstat -p -d

If you want to delete a printer on your machine:

$$ lpadmin -x Printer_name




**part of this has been taken from http://sumitgoel.me