Linux: paste and diff -b

tidbits recently of use to me:

• paste to put two files together by merging their columns, without the complications of join
• diff -b to ignore blank lines etc, when comparing how my new code is different from the old code.

Rohit Bhardwaj's talk on Android programming last night at NE-JUG

(from NEJUG talk last night: http://www.nejug.org/events/show/128)

http://dl.dropbox.com/u/8106990/Android_Cool_apps_built_by_developers_like_you_1UP.pdf

http://dl.dropbox.com/u/8106990/Android_Cool_apps_built_by_developers_like_you_2UP_BW.pdf

Just text notes here:

http://dl.dropbox.com/u/8106990/AndroidNotes.txt

Listing other dl.dropbox URL's for a zip of samples source code.

His twitter:

http://twitter.com/#!/rbhardwaj1

My notes:

• Each App has its own 'Linux User' so it can't poach security info.
• All the data locked in for that user.
• There are ways to share data between apps.
• APK 
• instead of EXE
• can be stored in SD-card
• testing: need to test with at least 50 devices
• use ADBridge
• autogenerated R.java has all References. 
• OnCreate(Bundle savedInstance)
• Honeycomb/Android 3 like iPad, multitasking
• Android marketplace $25 to sell your apps.

See also http://code.google.com/edu/android/index.html

Python: appending column to end of tab-separated csv

Given this input file:

$ cat list.csv
a       b       c
d       e       f
g       h       i

Using this code:

import os,csv

def test_fcn() :
    try:
        tabReader = csv.reader( open("list.csv", "rb"), delimiter='\t', quoting=csv.QUOTE_NONE )
        fd = open("out.csv", "wb+")
        tabWriter = csv.writer(fd, delimiter='\t', quoting=csv.QUOTE_NONE)
        if tabReader != None :
            for record in tabReader:
                record.append("new_thing")
                tabWriter.writerow(record)
        fd.close()
        return

    except Exception,e :
        print "Exception : " + str(e)
        
def main():
    test_fcn()

if __name__ == '__main__':
    import sys
    main(*sys.argv[1:])

Here's the output:

$ cat out.csv
a       b       c       new_thing
d       e       f       new_thing
g       h       i       new_thing

Linux: Using whereis to find ifconfig

If something isn't in default path you still may be able to find it with whereis:

$ ifconfig
bash: ifconfig: command not found
$ whereis ifconfig
ifconfig: /sbin/ifconfig /usr/share/man/man8/ifconfig.8.gz
$ /sbin/ifconfig
eth2 Link encap:Ethernet HWaddr ...



Linux: to grep for dash, use grep --

For example, to search for python code containing the string "-D":

grep -- -D *.py

From http://stackoverflow.com/questions/2427913/grepping-for-string-containing-dash

Linux: Getting a list of known hosts without all the key stuff


cut -d ' ' -f 1 ~/.ssh/known_hosts


Linux: In vi, to show line numbers do :set nu

:set nu

Turn off with

:set nonu

or

 :set nonumber

Other vi links so far:

• vi text wrap
• see tab and newline characters
• split screen (This doesn't always work.)

Python: Convert Python List to SQL "IN" List

    py_list=[123,2343,433,454]

    #convert the python list into a string to be used in SQL "IN" query
    sql_list=""
    quote = '\''
    for item in py_list:
        sql_list+= quote + item + quote

    query_string="SELECT ITEM FROM MY_TABLE WHERE MY_ID IN " + sql_list
    ...

Thank you, Janak.

Python IDE: PyScripter

Allen is using Eclipse.  Janak is using Stani's Python Editor.  I tried downloading Stani's some months back, but it never ran.  Janak says it needs configuring.

So I read A Beginner's Guide to IDE's, consulted http://wiki.python.org/moin/PythonEditors, and decided to go with the lightweight and "fast" single-language IDE PyScripter.

It downloaded and installed just fine.  I like that you can choose which version of Python to open it up with from the Open Program/PyScripter menu.  We're currently using 2.6, so I can look at our code in the IDE with 2.6 interpreting it.

Linux: uname -a tells you what version of Linux you're running

$ uname -a
Linux rhel54-64 2.6.18-164.el5 #1 SMP Tue Aug 18 15:51:48 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux

There are other options to get selected info. You can do a "man uname" to see them.