Basic unix commands

Find and grep

Unix Command Description

find . | grep -i app.jar

Lists all app.jar files in current directory case insensitive

find . | grep .svn | xargs rm -f

Find all files containing the pattern .svn in the current directory and delete them.

find /tmp -name core -type f -print | xargs /bin/rm -f

Find files named core in OR below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces.

grep git ~/.bash_history

Show all current git calls in the file .bash_history

grep -ir "main(String\[\] args)" .

Look for the string main(String[] args) in ALL files of the current directory
-i: case insensitive
-r: recursive

Current process

Unix Command Description

ps aux | grep -i java

Displays all current running processes containing java as name.

top -p 66939

Displays detailed view of the process with the given process ID.

kill -9 66939

kill processes with the id 66939

killall -s ssh

kill processes with the name ssh
-s: Show only what would be done, but do not send any signal.

Compress and encrypt with ZIP

Unix Command Description

zip -r -e FinalName SourceDirectory

Recursive compression of the SourceDirectory and encryption with a password provided by a terminal prompt.
-r: include all files and subdirectories.
-p: preserves modification times, access times, and modes from the original file.
FinalName: Resulting file name after compression and encryption.
SourceDirectory: Input folder.

unzip SourceDirectory

Uncompress (and decrypt) the SourceDirectory. If necessary a password has to be provided by a terminal prompt.


Unix Command Description

cp -r /src/dir/. /dest/dir/

Copies ALL files, including hidden files and the whole directory structure recursiv

scp LocalFile.example User@Host:Folder/DestinationFile.example

Copys LocalFile.example from your local machine to the host in DestinationFile.example

scp User@Host:/home/bakka/HostFile.example DestinationFile.example

Copys HostFile.example from the host to your local machine as DestinationFile.example

scp -rp sourcedirectory User@Host:/path

Copys sourcedirectory from your local machine to the host
-r: copy the directory recursive


Unix Command Description

ifconfig -a

Display information about all interfaces in the system

nslookup mucsgvpint64

Query Internet domain name servers

nmap -p 5432

Create and close one TCP connection to port 5432 to the host (e.g check data base connectivity)

netstat -a -n -p TCP

Shows network status with IP adresses and ports
-a: All connections
-n: Show adresses and ports as numbers
-p: Protokol: TCP

Inspect files

Unix Command Description

ls -ltr

list all files sorted by time as most recently modified are last displayed

ls -al | tee out.txt | grep test

tee reads standard input and writes it to both standard output and one or more files

file testfile

Inspects the testfile and displays an assumption about the file content, e.g.: index.html: HTML document text

tail -f *

Displays last lines of ALL files in current directory, waits for further input

diff file1 file2

compare files line by line

diff -arq folder1 folder2

recursive compare of folders
a: treat all files as text
r: recursive compare of subdirectories
q: output only whether files differ


Unix Command Description

shutdown -h now

halt and close down the system immediately, requires sudo

echo "myLine" >> file.txt

Write the String 'myLine' inside of the file file.txt

df -h

Displays statistics about the amount of free disk space in "Human-readable" output.

du -sh folderName OR fileName

Displays size in human readable format of folderName OR fileName

mkdir -p src/main/java

Creates a parent directory src, a child directory main and another child java

chown -R bakka /home/bakka

Change ownership of directory /home/bakka to user bakka ALL including files and subdirectories are affected.

tar zxfv file.tar.gz

tar process stream files
z: uncompress gunzip
x: extraxt
f: force overwrite existing
v: verbose

Bash environment

Unix Command Description


List ALL environment variables

whereis ssh

locate the program ssh

Platform dependent tools

OS X - Using pasteboard/clipboard

Command Description

pwd | pbcopy

(1) Copies current directory inside the clipboard

cd `pbpaste`

(2) changes directory to the value inside clipboard

Ubuntu Linux

Linux Command Description

dpkg -i package.deb

Installs debian package package.deb, requires sudo

apt-get update

Update debian package list

apt-get install ExmpPackage

Installs ExmpPackage

apt-get remove ExmpPackage

Removes ExmpPackage

apt-get purge ExmpPackage

Removes ExmpPackage and wipeouts any configuration

apt-get autoremove ExmpPackage

Removes obsolete dependencies from ExmpPackage.

Bash Configuration

Ubuntu Linux

Setting global environment variables for login and sub shells

Trivial definitions

A login shell is started on system boot process. It’s the one where the user is going to be authenticated by its credentials (username, password). All user specific configurations are loaded on this point for the user. Other shells started from this point, derive the settings from the login shell and are called sub shells (like the manual start of the terminal program that runs the shell in a window). To see another login shell you can leave your desktop with Ctrl + Alt + F1 and go back with Ctrl + Alt + F7. Another example of a login shell is the connection via ssh.

Lets configure some environment variables for the login shells as a system wide configuration.

/etc/profile: system-wide .profile file for the Bourne shell
# JDK 8 export
export JAVA_HOME='/home/bakka/java/jdk1.8.0_65' (1)
export PATH="$JAVA_HOME/bin:$PATH" (2)
  1. The use of single quotation marks for JAVA_HOME causes interpolation to be suppressed! Only single quotation marks within the URL need be escaped.

  2. Double quotation marks in the second assignment allow interpolation.

Verify this global setting for login shells via the command sh -l -c 'printenv JAVA_HOME' that should result in:


Ok that works, but what about the sub shells those have to derive the global setting from /etc/profile? We simple evaluate the /etc/profile file and execute it in the current context with the source command inside of .bashrc that is called on each sub shell creation for the current user.

~/.bashrc: executed by bash(1) for non-login shells.
source /etc/profile

Check this result with echo $JAVA_HOME that should return:



If .bashrc does not exist in your home folder create one and make sure it is referenced in ~/.profile like that:

# ~/.profile: executed by Bourne-compatible login shells.

if [ "$BASH" ]; then
  if [ -f ~/.bashrc ]; then
    . ~/.bashrc

As an alternative define source /etc/profile directly in ~/.profile.

Current folder in bash prompt

Prompt shows only current directory in ubuntu-bash.

export PS1='\u@\h:\W$ '

Bash Scripting

Simple loop

Loop: for each file that end with jpg rename the file to the current name with the prefix my.

for i in *.jpg; do mv "$i" "my.$i"; done