Shantanu's Blog

Database Consultant

June 26, 2013

 

Transpose data using python

# cat test.csv
name,height,weight
abc, 12,4
xyz, 6,4

I need to return the column values as list. So the names should return as a list with values like "abc, xyz"

with open('test.csv') as f:
    reader = csv.DictReader(f, delimiter=',')
    rows = list(reader)

names = [i['name'] for i in rows]
heights = [float(i['height']) if i['height'] else 0.0 for i in rows]
weights = [float(i['weight']) if i['weight'] else 0.0 for i in rows]

Labels:


 

Managing MySQL data in python

>>> import MySQLdb as db
>>> con = db.connect(user="foo", passwd="secret")
>>> cur = con.cursor()
>>> cur.execute('CREATE DATABASE chom;')

cur.execute ("SELECT name, category FROM animal")
rows = cur.fetchall ()
for row in rows:
    print "%s, %s" % (row[0], row[1])
print "%d rows were returned" % cur.rowcount

cur.execute ("""
CREATE TABLE animal
(
name CHAR(40),
category CHAR(40)
)
""")

http://www.cs.columbia.edu/~hgs/teaching/ap/examples/scripts_python_dbapi.pdf

Labels: ,


June 04, 2013

 

Kill processes

There are times when I check the process ID from "ps aux" command output and kill it. But it may take time to kill processes one at a time.
Easier way to kill multiple processes is by executing the following two functions.

function psgrep ()
{
ps aux | grep "$1" | grep -v 'grep'
}

function psterm ()
{
[ ${#} -eq 0 ] && echo "usage: $FUNCNAME STRING" && return 0
local pid
pid=$(ps ax | grep "$1" | grep -v grep | awk '{ print $1 }')
echo -e "terminating '$1' / process(es):\n$pid"
kill -SIGTERM $pid
}

You can add them to the .bash_profile so that these functions are available all the time. You can check the processes using "psgrep" function while killing them easy with "psterm".

# psgrep http

# psterm httpd
terminating 'httpd' / process(es):
31186
31187

Labels: ,


 

apache control

You can start apache with different directory using directive parameter

# httpd -k start -c “DocumentRoot /var/www/html_debug/”
If you want to go back to original configuration using the default DocumentRoot (/var/www/html), restart the Apache.
# httpd -k stop
# apachectl start

httpd -k start -e debug

Possible values you can pass to option -e are:
info
notice
warn
error
crit
alert
debug
emerg

Labels: ,


 

Managing history

// add date when the command was executed
export HISTTIMEFORMAT=’%F %T ‘

// ignore commands in history
export HISTIGNORE=”pwd:ls:ls –ltr:”
export HISTCONTROL=ignoredups
export HISTCONTROL=ignorespace

// clear all the previous history.
history -c

// disable history
export HISTSIZE=0

Labels: ,


 

Using command prompt to alter user

Using the export command we can change the linux command prompt to make it more informative. It is also possible to display the output of shell script as command prompt. For e.g. in the following example, when the disk space is 85% full, it will display a prompt.

export PS1="[\@] [`ifconfig | grep Bcast | awk '{print $2}' | awk -F':' '{print $2}'`] \$(diskfull.sh) > "

The new prompt will look something like this...

root@ip-10-158-57-83 disk full >

And the shell script:

cat /bin/diskfull.sh
#!/bin/sh

# set alert level 80% as default if no user input found
ALERT=${1:-95}

df -HP | grep -vE '^Filesystem|tmpfs|cdrom' | awk '{ print $5 " " $1 }' | while read output;
do
usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1 )
partition=$(echo $output | awk '{ print $2 }' )
if [ $usep -ge $ALERT ]; then
echo "disk full"
exit
fi
done

Labels: ,


June 01, 2013

 

Welcome infobright

Infobright is mysql compatible data ware house software. The free community version does not allow to insert / update /delete records. The only way to import data is to use "load data" statement. Here is a simple shell script that will copy the data from mysql to infobright. The table needs to be created in infobright manually. It is not part of this script because mysql datatypes and indexes needs to be modified.

#!/bin/sh

ibdata='test'
ibtable='window_way'

mysqlshow | awk '{print $2}' | while read dbname
do

rm -f /tmp/load.txt
rm -rf /tmp/$ibdata

time mysql -uroot -pPassWdsql $dbname -e"select *, database() into outfile '/tmp/load.txt' from $ibtable"

time mysql-ib -uroot -pPassWdIB $ibdata -e"set @BH_REJECT_FILE_PATH = '/tmp/$ibdata'; set @BH_ABORT_ON_COUNT = 1000; load data infile '/tmp/load.txt' into table $ibtable fields terminated by '\t' "

done

Labels:


Archives

June 2001   July 2001   January 2003   May 2003   September 2003   October 2003   December 2003   January 2004   February 2004   March 2004   April 2004   May 2004   June 2004   July 2004   August 2004   September 2004   October 2004   November 2004   December 2004   January 2005   February 2005   March 2005   April 2005   May 2005   June 2005   July 2005   August 2005   September 2005   October 2005   November 2005   December 2005   January 2006   February 2006   March 2006   April 2006   May 2006   June 2006   July 2006   August 2006   September 2006   October 2006   November 2006   December 2006   January 2007   February 2007   March 2007   April 2007   June 2007   July 2007   August 2007   September 2007   October 2007   November 2007   December 2007   January 2008   February 2008   March 2008   April 2008   July 2008   August 2008   September 2008   October 2008   November 2008   December 2008   January 2009   February 2009   March 2009   April 2009   May 2009   June 2009   July 2009   August 2009   September 2009   October 2009   November 2009   December 2009   January 2010   February 2010   March 2010   April 2010   May 2010   June 2010   July 2010   August 2010   September 2010   October 2010   November 2010   December 2010   January 2011   February 2011   March 2011   April 2011   May 2011   June 2011   July 2011   August 2011   September 2011   October 2011   November 2011   December 2011   January 2012   February 2012   March 2012   April 2012   May 2012   June 2012   July 2012   August 2012   October 2012   November 2012   December 2012   January 2013   February 2013   March 2013   April 2013   May 2013   June 2013   July 2013   September 2013   October 2013   January 2014   March 2014   April 2014   May 2014   July 2014   August 2014   September 2014   October 2014   November 2014   December 2014   January 2015   February 2015   March 2015   April 2015   May 2015   June 2015   July 2015   August 2015   September 2015   January 2016   February 2016   March 2016   April 2016   May 2016   June 2016   July 2016   August 2016   September 2016   October 2016   November 2016   December 2016   January 2017   February 2017   April 2017   May 2017   June 2017   July 2017   August 2017   September 2017   October 2017   November 2017   December 2017   February 2018   March 2018   April 2018   May 2018   June 2018   July 2018   August 2018   September 2018   October 2018   November 2018   December 2018   January 2019   February 2019   March 2019   April 2019   May 2019   July 2019   August 2019   September 2019   October 2019   November 2019   December 2019   January 2020   February 2020   March 2020   April 2020   May 2020   July 2020   August 2020   September 2020   October 2020   December 2020   January 2021   April 2021   May 2021   July 2021   September 2021   March 2022   October 2022   November 2022   March 2023   April 2023   July 2023   September 2023   October 2023   November 2023  

This page is powered by Blogger. Isn't yours?