Unix.md

Unix

Generate ssh keys

ssh-keygen -t rsa

Find processes running on a particular ports

netstat -vanp tcp | grep 8080
sudo netstat -tlnp | grep 8080
sudo netstat -lptu (see all listening ports)

Find process running on a particular port and show pid

lsof -i tcp:<port>

Kill a process by pid

kill -9 <pid>

Show the amount of disk space used and available

df

Display the amount of disk space used by the specified files and for each subdirectory

du

Find large directories and order

du -hs */ .*/ | sort -n

Simpler way of finding large directories and ordering

du -hsc * | sort -h

Add alias for command (redHat .bashrc else .bash_profile)

sudo nano/vi/vim .bashrc/.bash_profile
alias x='somecommand'

Copy from remote to local

scp username@192.168.1.111:/path/to/myfile.txt /Users/Jamie/local/path/to/myfile.txt

Find file/dir in root dir

# simple
find / -name somefilename
# directories only
find / -type d -name 'some_filename'
# prevent printing errors
find / type d -name 'some_filename' 2> /dev/null

Find files containing a given string

grep -rn '/path/to/somewhere/' -e "pattern"

Get a count of files in a given directory

find ./directory-name -type f | wc -l

Get count of lines in a given file

wc -l filename

View memory usage (simple view)

free -m

View detailed memory usage as well as CPU stats etc

top

Delete all files in dir (workaround for rm -rf * "argument list is too long")

find . -type f -delete

Find and delete empty files from current dir down

find . -type f -empty -delete -print

Zipping when argument list is too long (omit -xvf etc)

zip -r my.zip .

Zip a directory with password (-e => prompted after running command to add password)

zip -e myzipperoo.zip temp/*

Unpacking tar.gz (2 step)

gzip -d filename.tar.gz
tar -xvf filename.tar

Unpacking tar.gz (1 step)

tar -xzf filename.tar.gz

Install ifconfig if missing

sudo [yum|apt-get] install -y net-tools

Install telnet (non-Alpine/apk)

sudo [yum|apt-get] install -y telnet|telnet-server

Install telnet (Alpine)

apk update
apk add busybox-extras

Use nc (netcat) to quickly check connectivity with an external host

nc -v -z hostname port

Switch to root user and stay in same directory

sudo -s

Run this before running a bash script to show all executed steps (good for debugging bash scripts)

set -x

Open a port that displays a simple message (accessible via "curl -v localhost:4001")

echo "Hello, World"  | nc -l 4001

View all users

cat /etc/passwd

View last 1000 lines of a file

tail -n 1000 <filename>

Get tar.gz of Java8_171 from command line (wget)

wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2Ftechnetwork%2Fjava%2Fjavase%2Fdownloads%2Fjdk8-downloads-2133151.html; oraclelicense=accept-securebackup-cookie;" "http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz"

Revert to default shell

chsh -s bash

Check OS (use either of the below)

cat /etc/os-release
lsb_release -a
hostnamectl

echo output of command to file

echo `ls -l ../` >> out.txt

Filename to variable

filename=`basename "$0"`

Watch a process e.g. docker ps, refresh every second

watch -n1 'docker ps'

Find all unique lines in a file

sort -u test.txt

Find all lines with unique first column (-k1) with comma delimiter (-t,) - useful for sorting through csv files

sort -u -t, -k1,1 test.csv

vi/vim show line numbers

:set number

Find out when all files in a directory were last modified (in reverse order)

find directoryname/ -type f -printf '%TY-%Tm-%Td %TT %p\n' | sort -r

Trim all quotes from input

<input> | tr -d '"'

Find lines in file that do not contain a given string (grep -v) and send to another file

cat <input_file_name> | grep -v <string_to_ignore> > <output_file_name>

Add date and time to history command

export HISTTIMEFORMAT="%d/%m/%y %T "

Remove line from history

history -d line_number

Remove entire history

history -c

Gzip and keep local file

gzip -k filename

Result of previous command

$?

Set current directory to a varable

readonly dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

Bring in functions from another .sh file in a location relative to the script you're running

source ${dir}/otherfunctions.sh

base64 encode latest item on clipboard

pbpaste | base64

base64 decode latest item on clipboard

pbpaste | base64 -d

netcat (nc) check port on host

# -z (scan for port, without sending any data)
# -v (verbose)
nc -zv google.com 80

telnet check port on host

telnet google.com 80

Save output of command to a file

# Set the command to an environemnt variable (this helps preserve whitespaces and newlines etc.)
TEMP=`kubectl -n my_namespace get events --sort-by=.metadata.creationTimestamp | grep fail`
# Now echo this env var to a file making sure to wrap it in double quotes
echo "$TEMP" >> output.txt

Show all installed versions of Java (Mac)

/usr/libexec/java_home -V
or
mdfind -name 'java' | grep '/bin/java$'

Find a given string in sh files

find . -name '*.sh' -exec grep "some string you want to find" {} \;