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Saturday, 20. June 2009
tmpdir in MySQL
In MySQL, the tmpdir path is mainly used for disk-based sorts (if the sort_buffer_size is not enough) and disk-based temp tables.

You can configure a slave with tmpdir=/dev/shm

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Wednesday, 13. May 2009
Install SQLite
$ # As of March 2009, the latest version was 3.6.11.
$ wget www.sqlite.org
$ tar xzf sqlite-amalgamation-3.6.11.tar.gz
$ cd sqlite-3.6.11
$ ./configure && make
$ sudo make install

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Monday, 11. May 2009
Using binlogs to update table
It is very interesting to know about how to extract statements from binlogs.

mysqlbinlog --start-datetime="`date +%Y-%m-%d' '%H:00:00 -d\"1 hour ago\"`" --stop-datetime="`date +%Y-%m-%d'
'%H:00:00`" mysql-bin.* | awk '/tbl_company/,/;/' | replace tbl_company mydb.tbl_company | mysql -h 172.29.0.0 -uroot -pPasswd mydb

I have not tested it, but guess it should work as expected.

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Monday, 4. May 2009
awk power
$ cat salaries
Yvette van der Hoff 100000
Sarack Abama 400000
Bernie Madoff 0
John Q. Public 20000

$ awk '{print $NF, $0}' salaries | sort -nr -k1,1 | cut -d" " -f2-
Sarack Abama 400000
Yvette van der Hoff 100000
John Q. Public 20000
Bernie Madoff 0

$ awk -F '\t' -v 'OFS=\t' '{print $4, $3, $5, $2, $1}' data.txt
POP. COUNTY GOVT. CITY STATE
123 Gila Mayor Ely AZ
345 Lolo Sheriff Alma CA
22 El Paso Bubba Leroy TX

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Sunday, 3. May 2009
skip networking in MySQL
When there is maintenance work to be carried on the database server, you can simply skip networking so that no connection from any other server from the network will be accepted.
Simply enter the following in /etc/my.cnf:

[mysqld]
# Prevent network access to MySQL.
skip-networking

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Saturday, 2. May 2009
Saving data to text file
sqlite> .mode list
sqlite> .separator |
sqlite> .output test_file_1.txt
sqlite> select * from tbl1;
sqlite> .exit
$ cat test_file_1.txt
hello|10
goodbye|20
$

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Thursday, 30. April 2009
Silent mode in Linux
Sick of your computer speaker beeping like a demented Morse code machine whenever you type something wrongly? Teach it the sound of silence: run the command
setterm -blength 0
to mute the alarm bell no matter what kind of terminal you're typing into.
If you want it to happen every time you start a terminal, just add the command to your .bash_profile file.

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Monday, 13. April 2009
valid date
validdate.sh script will look like this...

#!/bin/sh
userdate=$1
date -d $userdate &> /dev/null
if [ $? -ne 0 ] ; then
echo You entered an invalid date, $userdate
else
echo The date $userdate is valid
fi

# sh validdate.sh 2009-33-44
You entered an invalid date, 2009-33-44

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Tuesday, 7. April 2009
IP addresses from access log
generate a list of IP address along with the number of times each was encountered and sort

cat access_log | awk '{print $1}' | sort | uniq -c | sort -nr

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Monday, 6. April 2009
Backup a directory
#!/bin/sh
tar czvf $1.$(date +%Y%m%d-%H%M%S).tgz $1
exit $?

The arc script accepts a single file or directory name as a parameter and creates a compressed archive file with the current date embedded into the resulting archive file's name.

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Recent updates
tmpdir in MySQL In MySQL, the tmpdir path is mainly used for disk-based sorts (if...
by shantanuo (2009.06.20, 07:22)
Install SQLite $ # As of March 2009, the latest version was 3.6.11. $ wget...
by shantanuo (2009.05.13, 19:24)
Using binlogs to update table It is very interesting to know about how to extract...
by shantanuo (2009.05.11, 21:43)
awk power $ cat salaries Yvette van der Hoff 100000 Sarack Abama 400000 Bernie Madoff...
by shantanuo (2009.05.04, 20:07)
skip networking in MySQL When there is maintenance work to be carried on the database...
by shantanuo (2009.05.03, 21:04)
Saving data to text file sqlite> .mode list sqlite> .separator | sqlite> .output test_file_1.txt sqlite>...
by shantanuo (2009.05.02, 20:31)
Silent mode in Linux Sick of your computer speaker beeping like a demented Morse code...
by shantanuo (2009.04.30, 12:51)
valid date validdate.sh script will look like this... #!/bin/sh userdate=$1 date -d $userdate &> /dev/null...
by shantanuo (2009.04.13, 15:44)
IP addresses from access log generate a list of IP address along with the number...
by shantanuo (2009.04.07, 12:04)
Backup a directory #!/bin/sh tar czvf $1.$(date +%Y%m%d-%H%M%S).tgz $1 exit $? The arc script accepts...
by shantanuo (2009.04.06, 15:47)
Time Zone error on slave Last_Error: Error 'Unknown or incorrect time zone: 'Etc/UTC'' on query....
by shantanuo (2009.03.30, 13:05)
pager to md5sum When optimizing queries by rewriting them to different forms that should return...
by shantanuo (2009.03.30, 13:03)
setting at jobs # at -v 03:00 -f /root/shantanu/testat.sh > /root/shantanu/testat_result.txt 2>&1 # atq 7...
by shantanuo (2009.03.13, 10:07)
better code `test -s /var/log/mailme.txt` if [[ $? -eq 0 ]] ; then The above...
by shantanuo (2009.03.10, 18:15)
read .csv file #!/bin/sh awk -F"," '{print $1,$2}' read1.txt | while read var1 var2 do...
by shantanuo (2009.03.10, 18:03)
common crontab entry 30 0 * * * updatedb > /dev/null 2>&1 # Clock synchronization...
by shantanuo (2009.03.10, 10:20)
Declare your assets! The declare command can be helpful in identifying variables, environmental or otherwise....
by shantanuo (2009.03.01, 18:48)
Innodb troubleshooting When you have your mysql up and running, just connect to any database...
by shantanuo (2009.02.26, 12:59)
Watch replication $ watch --interval=1 --differences 'mysql -uuser -ppassword -e "show slave status\G"'
by shantanuo (2009.02.25, 18:30)
findtable shell script # vi /bin/findtable #!bin/sh mysql -e"select TABLE_SCHEMA, TABLE_NAME, ENGINE, TABLE_ROWS, CREATE_TIME FROM...
by shantanuo (2009.02.05, 17:31)
processor info Gather information about the processor. This is easily done as follows: # cat...
by shantanuo (2009.01.20, 19:44)
Help Me! You can use the mysql client to perform lookups in the MySQL manual....
by shantanuo (2009.01.02, 20:33)
Show only PHP errors Open /etc/php.ini file # vi /etc/php.ini Set error_reporting as follows: error_reporting...
by shantanuo (2008.12.31, 16:46)
optimize all tables mysql -e"SELECT CONCAT('OPTIMIZE TABLES ', GROUP_CONCAT(TABLE_SCHEMA, '.', TABLE_NAME ORDER BY TABLE_SCHEMA, TABLE_NAME...
by shantanuo (2008.11.11, 17:14)
Unix cheatsheets Cheat sheet act as a reference tool which provides cut and paste kind...
by shantanuo (2008.11.08, 19:30)

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