sathish-io

MySQL Table names in Linux is case sensitive. 

To disable it, set property lower_case_table_names=1 in  /etc/my.cnf file under "[mysqld]" section, as shown below, 

==================
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks

sathish-io

Here is the command to find out the process # that is listening at the givne port(say 8080) in on Mac OS X,

lsof -n -i4TCP:8080 | grep LISTEN

this will return below sample o/p,

java    41038 user1   54u  IPv6 0x68e4c014dcuy8y0      0t0  TCP *:http-alt (LISTEN)

sathish-io

How to check high response HTTP calls from JBoss access log file

Response time is last field in the access log, and below command will show calls that took more than 5 seconds.

cat  access.log | awk -F " " '{ if ($NF > '5') {print $0}}' 

sathish-io

Find files that are older than 1 day with file name 'LOGFILE', and delete them.

find /var/log/ -type f -mtime +1  -name '*LOGFILE*' -exec rm {}  \;

We can put this delete command in a script say deleteOldLogs.sh and add it in cron entry to run every day,

crontab -l

0 0 * * * /usr/sathish/Scripts/deleteOldLogs.sh

sathish-io

some times, you are in need of doing DML operation that involves strings with & sign in it. 
Oracle sql clients treats this as a substitution variables and prompts you to enter value.

For example when you run below select statement; it prompts you to enter value for "T".
select 'A&T' from dual;

To disable this you can disable substitution variables for your session using "SET DEFINE OFF"
Note: & is the default value for DEFINE.

SET DEFINE OFF

sathish-io

NET START postgresql-x64-9.3 (64-bit windows)
NET STOP postgresql-x64-9.3 (64-bit windows)

NET START postgresql-9.3 (32-bit windows)
NET STOP postgresql-9.3 (32-bit windows)


Note: This is for Windows 7. Replace 9.3  with your version of PostgreSQL version.

sathish-io

To troubleshoot memory leak related issues in java based application, we are in need of analyzing the JVM heap dump to understand potential objects that are causing the problem. 

To take the heap dump below command helps, 

jmap -dump:format=b,file=jvm_heap_dump.hprof {PID}

This will create file with name - jvm_heap_dump.hprof

Then, we can use eclipse Memory Analyzer(MAT) to analyze the dump.

sathish-io

To download souce,
mvn dependency:sources 

To start spring boot app:
mvn spring-boot:run

To run single test:
mvn -Dtest=TestCircle test

To remote debug maven test case, run with below option,

sathish-io

Basic postgresql commands:


\l  - to list all database.

\db - to list all tables in a db.

\d <tablename> - to describe a table

Create new database

sathish-io

AWK script to get min, max, sum, average, standard deviation for numbers:

cat data.txt | awk -F ":" 'BEGIN {max = 0; min = 999999; sum = 0; sumsq = 0} { x= ($NF + 0); sum += x; sumsq += x*x; if(x > max)max = x; if(x < min) min = x}  END { print "Min: ", min,  " Max: ",max, " Sum: ", sum, " Average: ", sum/NR , " Std Dev: ", sqrt(sumsq/NR - (sum/NR)^2) }'  

Assume you have data.txt that has following data set,
2
3
6
8
11