denitram

#---To change the passphrase on your default rsa key:
$ ssh-keygen -p -f ~/.ssh/id_rsa

#---Keep alive
~/.ssh/config
Host *
  ServerAliveInternal 30
  TCKeepAlive yes

denitram

# List installed packages

# List all services
systemctl list-unit-files

denitram

#--- Commandline history substitution

* Replace old by new in prevous command
^old^new
^old^new is equivalent to !!:s/old/new

* Replace globally
!!:gs/old/new

#--- Batch renaming file

denitram

 * quick and dirty
 for i in `ls` ; do mv "$i" "$(echo $i | tr A-Z a-z)"; done
 
 * beter version
 for i in $(find . -type f -name "*[A-Z]*"); do mv "$i" "$(echo $i | tr A-Z a-z)"; done

-name "*[A-Z]*" ensures that only files with capital letters are found. For example, if files with only lowercase letters are found and moved to the same file, mv will display the are the same file error.
Thanks to Steve see: http://stackoverflow.com/questions/13051871/change-filenames-to-lowercase-in-ubuntu-in-all-subdirectories

denitram

# Add the first line of file1 at the top of file2
$ h=head -n 1 file2
$ sed -i "1s/^/$h \n/" file2

denitram

java -cp ~/.m2/repository/org/hsqldb/hsqldb/2.2.8/hsqldb-2.2.8.jar  org.hsqldb.util.DatabaseManager

denitram

#!/bin/bash

# Set proxy settings in Ubuntu for eclipse, maven and apt

#### variables
ECLIPSE_SETTINGS_DIR="/home/martine/apps/springsource/sts-3.4.0.M1/configuration/.settings/"
ECLIPSE_SETTINGS_FILE="org.eclipse.core.net.prefs"
ECLIPSE_SETTINGS_PROXY="org.eclipse.core.net.prefs-PROXY"
ECLIPSE_SETTINGS_NOPROXY="org.eclipse.core.net.prefs-NOPROXY"
ECLIPSE_SETTINGS=$ECLIPSE_SETTINGS_DIR$ECLIPSE_SETTINGS_FILE

denitram

# First, make a dump of the database without data (-s)
$ pg_dump -h localhost -U username -Fc -s -f db_dump dbName

# Create a list of the functions
$ pg_restore -l db_dump | grep FUNCTION > function_list

# Restore the functions in an other database
$ pg_restore -h localhost -U username -d other-dbName -L function_list db_dump

denitram

-- Viewing current PostgreSQL queries
-- source: http://chrismiles.info/systemsadmin/databases/articles/viewing-current-postgresql-queries/
SELECT datname,pid,query,query_start FROM pg_stat_activity ORDER BY query_start ASC;

-- top-like view of current queries, grouped by how many of the same query are running at that instant and the usernames belonging to each connection.
SELECT count(*) as cnt, usename, current_query FROM pg_stat_activity GROUP BY usename,current_query ORDER BY cnt DESC;

-- List databases creation dates
SELECT (pg_stat_file('base/'||oid ||'/PG_VERSION')).modification, datname FROM pg_database ORDER BY modification;
SELECT (pg_stat_file('base/'||oid ||'/PG_VERSION')).modification, datname FROM pg_database ORDER BY datname;

denitram

http://net.tutsplus.com/tutorials/other/8-regular-expressions-you-should-know/

# insert a new line with '<null\>' as content every 6th line between lines 100 and 2000
100,2000s/\v(.*\n){6}/\0\<null\/\>\r/g
see http://stackoverflow.com/questions/10413906/how-to-add-a-line-after-every-few-lines-in-vim

# delete blank lines
:g/^$/d

# join all lines