LINUX , UNIX , BASH AND CYGWIN TIPS AND TRICKS

LINUX , UNIX , BASH AND CYGWIN TIPS AND TRICKS

This document contains linux unix bash cygwin related code snippets

1. FILE AND DIRS MANAGEMENT

This section contains tips and tricks on files and dirs management.

1.1. how-to search for string recursively in bash

Run the following command

for file in `find . \( -name '*.pm' -or -name '*.pl' \) -type f `; do grep -nHP boo $file ; done ;

1.2. how-to create a symlink

how-to create a symlink

# START === create symlink

export link_path=/vagrant

export target_path=/mnt/hgfs/vagrant

mkdir -p `dirname $link_path`

unlink $link_path

ln -s "$target_path" "$link_path"

ls -la $link_path;

# STOP === create symlink

1.3. how-to search and replace line feeds in a selection in excel

1. Select the cells.
2. Ctrl + H to present the find and replace dialog
3. For search: press the Alt num and from the Num keyboard type : 013 or 011
4. For replace: type the char to replace with
5. Replace all the occurrencies by : Alt + A

1.4. how-to search and replace strings in file contents recursively

In order to search and replace strings in the file and dir contents perform the copy paste the following code in your bash shell terminal.

# START -- how-to search and replace recursively

export dir=/var/company/3rdparty/docs/docx;

export to_search="emric"

export to_replace="t24"

#-- search and replace in file contents

find "$dir/" -type f -exec perl -pi -e "s#$to_search#$to_replace#g" {} \;

find "$dir/" -type f -name '*.bak' | xargs rm -f

# STOP  -- how-to rename files recursively

1.5. how-to search and replace strings in file and dirnames recursively

In order to search and replace strings in the file and dir paths perform the copy paste the following code in your bash shell terminal.

# START -- how-to search and replace recursively

export dir=/var/company/3rdparty/docs/docx;

export to_search="emric"

export to_replace="t24"

#-- search and replace in file names

find "$dir/" -type d |\

perl -nle '$o=$_;s#'"$to_search"'#'"$to_replace"'#g;$n=$_;`mkdir -p $n` ;'

find "$dir/" -type f |\

perl -nle '$o=$_;s#'"$to_search"'#'"$to_replace"'#g;$n=$_;rename($o,$n) unless -e $n ;'

2. PACKING AND UNPACKING

Bunch of commands for packing and unpacking on Linux

2.1. how-to unpack a *.tar.gz package

Run the followint commands in the bash shell:

export dir=<>

cd $dir

# upack !!!

gzip -dc *.tar.gz | tar xvf -

2.2. how-to unpack a tar package

how-to unpack a tar package

#how-to unpack tar file

tar xvf $file

3. LINUX HARDWARE

3.1. how-to check the type of processors on the System

how-to check the type of processors on the System

cat /proc/cpuinfo | less

4. LINUX NETWORKING

4.1. how-to check which ports are listening

how-to check which ports are listening + others netstta

# which processes are listening on my system

netstat --tcp --listening --programs

netstat --tcp

netstat --route

4.2. how-to implement public private key authentication - pkk

Read the comments

You migth wanto to:

export ssh_usesr=some_user_name

export ssh_server=some_server_dns_or_ip

4.2.1. how-to implement rsa public private key authentication

Start on the client , check the comments when to move on the server.

# START === how-to implement public private key ( pkk ) authentication

# create pub priv keys on server

# START copy

ssh-keygen -t rsa

# copy the rsa pub key to the ssh server

scp ~/.ssh/id_rsa.pub $ssh_user@$ssh_server:/home/$ssh_user/

# STOP copy 

# Hit enter twice

# START copy

cat id_rsa.pub >> ~/.ssh/authorized_keys

cat ~/.ssh/authorized_keys

chmod -v 0700 ~/.ssh

chmod -v 0600 ~/.ssh/authorized_keys

chmod -v 0600 ~/.ssh/id_rsa

chmod -v 0644 ~/.ssh/id_rsa.pub

find ~/.ssh -exec stat -c "%U:%G %a %n" {} \;

rm -fv ~/id_rsa.pub

# STOP COPY

4.2.2. how-to implement dsa public private key authentication

Start on the client , check the comments when to move on the server.

# START copy

ssh-keygen -t dsa

# STOP copy 

# Hit enter twice

# START copy

cat id_dsa.pub >> ~/.ssh/authorized_keys

cat ~/.ssh/authorized_keys

chmod -v 0700 ~/.ssh

chmod -v 0600 ~/.ssh/authorized_keys

chmod -v 0600 ~/.ssh/id_dsa

chmod -v 0644 ~/.ssh/id_dsa.pub

find ~/.ssh -exec stat -c "%U:%G %a %n" {} \;

rm -fv ~/id_dsa.pub

# STOP COPY

# STOP === how-to implement public private key authentication

5. BASH

5.1. how-to use while loop in bash

This is an example usage of the while loop in bash

find `pwd` | { while read -r file ; do echo "$file" ; done ; }

5.2. how-to use for loop in bash

This is an example usage of the while for in bash. Note the find command herewith searches for 2 types of files

for file in `find / -type f \( -name "*.pl" -or -name "*.pm" \) -exec file {} \; | grep text | perl -nle 'split /:/;print $_[0]' `; do grep -i --color -nH 'string_to_search'  $file ; done ;