Bash for Everyone — Part 2


Part-2 — Learn Core Unix Commands.

3. One-liners

4. References

5. Closing gifs!

Learn Basic Unix Commands.

Working with commands

type — Display’s commands type
man type //Type Command manual page
type commands
which — Display which program will be executed.
man which //Which command manual p
which ls
help — Get help
help cd
mkdir --help
man — Display manual pages
info — Display commands info entry
man info
info coreutils
whatis — very brief description of the command.
man whatis
whatis ls
alias — Create an alias for a command.
alias l.='ls -d .* --color=tty'
alias ll='ls -l --color=tty'
alias ls='ls --color=tty'
unalias which //removing alias

Exploring the file system Commands.

ls — list directory contents
man ls

Useful ls Commands

ls -lt --reversels
ls -li
ls > list.txt
ls -l
ls -l "some_file"
lsof — list open files
pwd — Return working directory name.
man pwd
file — Determine file types
man file
file filename
more — file perusal filter for crt viewing
man more
less — View file content

Manipulating files and directories Commands.

cp — copy files and directories.
man cp
cp file.html /usr/local/bin
mv — move and rename files and directories.
man mv
mv file.html /usr/localbin //moving files
mv file.html file2.html //renaming files.
mkdir — create directories
man mkdir
mkdir somedirectory
mkdir dir1 dir2 dir3
rm — remove files and directories

Caution: Be careful with rm

man rm
rm file.txt
rm -i //interective - if this option is not defined, rm will delete files silently.
rm -r //recursive recursively delete directories.
rm -f //force delete.
rm -v //Display informative messages.
rm -rf file1 dir1 //if nither file1 or dir1 exists rm will countinue silently.

Redirection Commands

Redirection makes it possible to control where the output of command goes to, and where the input of command comes from.

stdin - standard input stream (eg- keyboard)
stdout - standard output stream (eg- monitor)
stderr - standard error output.
# Below cat-command will execute and redirect its error to (stderr) #to the bit bucket
cat file.txt 2>/dev/null
# below echo-command will execute and redirect its normal outout (stdout).
echo "there was an error" 1>&2
cat — concatenate files
man cat #Manual page
cat 1.txt 2.txt > new.txt
cat >new.txt 1.txt 2.txt
>new.txt cat 1.txt 2.txt
sort — Sort or merge records (lines) of text and binary files.
man sort
cat -n file.txt // file cat with no of lines.
cat company_ip | sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n ipaddr.list

Wow, that’s ugly. Here it is in the old format:

cat company_ip | sort -t. +0n -1 +1n -2 +2n -3 +3n -
uniq — report or omit repeated lines
man uniq
grep — print matching a pattern
man grep
grep root /etc/passwd
grep -n root /etc/passwd
grep -v bash /etc/passwd | grep -v nologin
grep -c false /etc/passwd
grep -i ps ~/.bash* | grep -v history
wc — print newline, word, and byte count for each file
man wc
head — output first part of the file
tail — output last part of the file

Permissions Commands

id — Display user identity
man id
chmod — change a file’s mode
man chmod
chmod u+x
chmod +x
su — Substitute user identity or run the shell as another user
man su
sudo — Execute a shell as another user
man sudo
passwd — Modify a user’s password
man passwd

Processes Commands

ps — Report current processes
ps x
ps aux
ps -ef
ps -ef | grep stuck_process
kill -9 5607

When a process starts up several instances, killall might be easier. It takes the same option as the kill command but applies on all instances of a given process.

top — Display task
bg — put a job in the background
fg — put a job in the foreground
kill — send a signal to a process
killall — kill processes by name

Environment commands

printenv — print all or part of the environment

Env and printenv commands used to display the environment variable.

printenv or env
man printenv
printenv | less
printenv USER
set — set shell options
set | less
set -o // display all shell options
Vim — Vi IMproved. a programmer’s text editor.
man vim

Benefits of using vim

vim is always available & vim is lightweight and fast

vi filname-txt
Enter "i" to edit
:q to exit and save
:q! to force exit and save
o - The line below the current line.
O - The line above the current line.

if interested. good read

Networking Commands —

Important networking files within the local machine.

  • /etc/hosts — Name to the Ip address
  • /etc/networks — Network name to the IP address
  • /etc/protocol — Protocol name to the Protocol number.
  • /etc/services — TCP/UDP names to the port number.
ping — Send an ICMP ECHO_REQUEST to network hosts
man ping
traceroute — Print the route packets trace to a network host, Route taken by packets to a specific Ip Address.
man traceroute
Dig — DNS lookuup Utility
netstat — Show network status, what connection is active between the local machine and another network machine.
man netstat
netstat -ie
netstat -r
netcat — Netcat is a simple Unix utility which reads and writes data across network connections,
Iptable — administration tool for IPv4/IPv6 packet filtering and NAT
IP — IP is the transport layer protocol used by the Internet protocol family.
SSH — Secure Shell
wget — The non-interactive network downloader.
man wget
curl — tranfer a URL
man curl

Getting subdomains from curl using

curl -s\?domain\ | jq '.[].dns_names[]' | sed 's/\*\.//g' | tr -d "\"" | sort -u

Cool bash_profile by Behrouz Sadeghipour

you can add the recon_profile in bash_profile present in the root directory.

you can also customize it according to your need.

Searching for files commands —

locate — locate the file by name
man locate
locate bin/zip
locate zip | grep bin
find — search for filesman find
find ~
find ~ | wc -l
find ~ -type d | wc -l
find ~ -type f | wc -l
find ~ -type f -name "*.JPG" -size +1M | wc -l 840

text processing commands,

cut — cut out a selected portion of each line of a file.

man cut
sed — Stream Editor is used to perform basic transformation on read text from a file or a pipe. sed is also sometimes known as bash editor.

awk — pattern-directed scanning and processing language

AWK: Effective AWK Programming: A User’s Guide for GNU Awk

the basic function of awk is to search files for lines or other text unit text containing one or more pattern. when a line matches one of the patterns, special action is performed on that line.

awk 'EXPRESSION { PROGRAM }' file(s)

The variables $1, $2, $3, …, $N hold the values of the first, second, third until the last field of an input line. The variable $0 (zero) holds the value of the entire line.

man awk
ls -l | awk '{ print $5 $9 }'
history | awk 'BEGIN {FS="[ \t]+|\\|"} {print $3}' | sort | uniq -c | sort -nr | head
Remove duplicate lines: awk '!a[$0]++'
Parallel —

We can use the parallel command to resolve the multiple javascript URLs present in a text file.

we can use TomNomNom way back URL to get javascript files URLs.

waybackurls | grep ".js" > deliveroo-js.txt
cat deliveroo-js.txt | parallel -j50 -q curl -w 'Status:%{http_code}\t Size:%{size_download}\t %{url_effective}\n' -o /dev/null -sk
Thanks to Bharat from Appsecco.

More commands

clear — clear the terminal screen.
man clear
History — Display the content of the history list
histroy | less
!88 - bash will expand “!88” into the contents of the 88th line in the history list
!! - Repeat the last command

Display most used commands

history | awk 'BEGIN {FS="[ \t]+|\\|"} {print $3}' | sort | uniq -c | sort -nr | head
Git — the stupid content tracker

Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both

high-level operations and full access to internals.


ASN — An autonomous system number (ASN) is a unique number assigned to an autonomous system (AS) by the Internet Assigned Numbers Authority (IANA).

ASN Example : - AS63086

CIDR(Classless Inter-Domain Routing or supernetting ) — is a way to allow more flexible allocation of Internet Protocol (IP) addresses than was possible with the original system of IP address classes.

A CIDR network address looks like this under IPv4:

Get CIDR from ASN numbers.

whois -h -- '-i origin AS63086' | grep -Eo "([0-9.]+){4}/[0-9]+" | head

CIDR to IP addresses using nmap

nmap -sL | grep "Nmap scan report" | awk '{print $NF}'

Finding Up hosts using NMAP.

nmap -sP -oG uber-ips.txt

Grep fro UP hosts only.

cat uber-ips.txt | grep Up | cut -d" " -f2

Saving UP hosts as uber-up-hosts.txt

Running masscan on uber-up-hosts.txt

masscan -iL uber-up-hosts.txt -p80,443,8080,8000,9000,8888,9999 --rate 10000 --open

Find your IP address using the command line:

/sbin/ifconfig -a | awk '/(cast)/ { print $2 }' | cut -d':' -f2 | head -1

Pulling IP address from a file.

grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'

Subdomains from hacker target

curl -s | cut -d',' -f1 | sort -u

Subdomains from Threatcrowd

curl -s | jq -r '.subdomains | .[]' | sort -u

Subdomains from Certspotter

curl -s\?domain\ | jq '.[].dns_names[]' | sed 's/\*\.//g' | tr -d "\"" | sort -u

Subdomain from

curl -s | sed '/crt/d' | sed 's/<\/\?[^>]\+>//g' | tr -d ' ' | sed 's/  */ /g' | sed 's/\*\.//g' | sed 's/\%\.//g' | sed -e '1,2d' | sort -u | uniq | grep hackerone | sed '/IdentityLIKE/d'

subdomains from Archive.

curl -s "**&output=text&fl=original&collapse=urlkey" |sort| sed -e 's_https*://__' -e "s/\/.*//" -e 's/:.*//' -e 's/^www\.//' | sort -u

cat deliveroo-domains.txt | filter-resolved > deliveroo-domains-resolved.txt

fetch titles of the subdomains from a list using httprobeand get-title

cat deliveroo-domains.txt | httprobe | get-title

Fetching interesting URL from waybackmachine

echo | waybackurls | tee test.txt | urinteresting

Subdomain from SSL certificates.

true | openssl s_client -connect 2> /dev/null | openssl x509 -noout -text 2> /dev/null | grep DNS: | sed 's/ DNS://g' | sed 's/ //g' | sed 's/,/\'$'\n/g'

Command line basic shortcuts

ctrl + a - move cursor to the begining of the line
ctrl + e - move cursor to the end of the line.
Alt+f - move one word forward
Alt+b Move cursor one work backword
ctrl+l- clear the clean (clear command alternative)

Personal Aliases —

these are the only tip of the iceberg,

more one-liners?

practice and make one-liners according to your need.


Thanks to all of the following peoples for creating awesome content.

Bash Cookbook by Carl Albing, JP Vossen, and Cameron Newham
The Linux Command Line by William Shott
Penetration Testing with the Bash Shell by Keith Makan

Closing Gifs.


Until Next Time!