Common commands

Tool: terminal

Reload shell without exit

exec $SHELL -l

Close shell keeping all subprocess running

disown -a && exit

Exit without saving shell history

kill -9 $$
unset HISTFILE && exit

Perform a branching conditional

true && echo success
false || echo failed

Pipe stdout and stderr to separate commands

some_command > >(/bin/cmd_for_stdout) 2> >(/bin/cmd_for_stderr)

Redirect stdout and stderr each to separate files and print both to the screen

(some_command 2>&1 1>&3 | tee errorlog ) 3>&1 1>&2 | tee stdoutlog

List of commands you use most often

history | \
awk '{CMD[$2]++;count++;}END { for (a in CMD)print CMD[a] " " CMD[a]/count*100 "% " a;}' | \
grep -v "./" | \
column -c3 -s " " -t | \
sort -nr | nl |  head -n 20

Sterilize bash history

function sterile() {

  history | awk '$2 != "history" { $1=""; print $0 }' | egrep -vi "\
curl\b+.*(-E|--cert)\b+.*\b*|\
curl\b+.*--pass\b+.*\b*|\
curl\b+.*(-U|--proxy-user).*:.*\b*|\
curl\b+.*(-u|--user).*:.*\b*
.*(-H|--header).*(token|auth.*)\b+.*|\
wget\b+.*--.*password\b+.*\b*|\
http.?://.+:.+@.*\
" > $HOME/histbuff; history -r $HOME/histbuff;

}

export PROMPT_COMMAND="sterile"

Look also: A naive utility to censor credentials in command history.

Quickly backup a file

cp filename{,.orig}

Empty a file (truncate to 0 size)

>filename

Delete all files in a folder that don't match a certain file extension

rm !(*.foo|*.bar|*.baz)

Pass multi-line string to a file

# cat  >filename ... - overwrite the file
# cat >>filename ... - append to a file
cat > filename << __EOF__
data data data
__EOF__

Edit a file on a remote host using vim

vim scp://user@host//etc/fstab

Create a directory and change into it at the same time

mkd() { mkdir -p "$@" && cd "$@"; }

Convert uppercase files to lowercase files

rename 'y/A-Z/a-z/' *

Print a row of characters across the terminal

printf "%`tput cols`s" | tr ' ' '#'

Show shell history without line numbers

history | cut -c 8-
fc -l -n 1 | sed 's/^\s*//'

Run command(s) after exit session

cat > /etc/profile << __EOF__
_after_logout() {

  username=$(whoami)

  for _pid in $(ps afx | grep sshd | grep "$username" | awk '{print $1}') ; do

    kill -9 $_pid

  done

}
trap _after_logout EXIT
__EOF__

Generate a sequence of numbers

for ((i=1; i<=10; i+=2)) ; do echo $i ; done
# alternative: seq 1 2 10

for ((i=5; i<=10; ++i)) ; do printf '%02d\n' $i ; done
# alternative: seq -w 5 10

for i in {1..10} ; do echo $i ; done

Simple Bash filewatching

unset MAIL; export MAILCHECK=1; export MAILPATH='$FILE_TO_WATCH?$MESSAGE'

Tool: busybox

Static HTTP web server

busybox httpd -p $PORT -h $HOME [-c httpd.conf]

Tool: [mount](https://en.wikipedia.org/wiki/Mount_(Unix))

Mount a temporary ram partition

mount -t tmpfs tmpfs /mnt -o size=64M

• -t - filesystem type

• -o - mount options

Remount a filesystem as read/write

mount -o remount,rw /

Tool: [fuser](https://en.wikipedia.org/wiki/Fuser_(Unix))

Show which processes use the files/directories

fuser /var/log/daemon.log
fuser -v /home/supervisor

Kills a process that is locking a file

fuser -ki filename

• -i - interactive option

Kills a process that is locking a file with specific signal

fuser -k -HUP filename

• --list-signals - list available signal names

Show what PID is listening on specific port

fuser -v 53/udp

Show all processes using the named filesystems or block device

fuser -mv /var/www

Tool: lsof

Show process that use internet connection at the moment

lsof -P -i -n

Show process that use specific port number

lsof -i tcp:443

Lists all listening ports together with the PID of the associated process

lsof -Pan -i tcp -i udp

List all open ports and their owning executables

lsof -i -P | grep -i "listen"

Show all open ports

lsof -Pnl -i

Show open ports (LISTEN)

lsof -Pni4 | grep LISTEN | column -t

List all files opened by a particular command

lsof -c "process"

View user activity per directory

lsof -u username -a +D /etc

Show 10 largest open files

lsof / | \
awk '{ if($7 > 1048576) print $7/1048576 "MB" " " $9 " " $1 }' | \
sort -n -u | tail | column -t

Show current working directory of a process

lsof -p <PID> | grep cwd

Tool: [ps](https://en.wikipedia.org/wiki/Ps_(Unix))

Show a 4-way scrollable process tree with full details

ps awwfux | less -S

Processes per user counter

ps hax -o user | sort | uniq -c | sort -r

Show all processes by name with main header

ps -lfC nginx

Tool: [find](https://en.wikipedia.org/wiki/Find_(Unix))

Find files that have been modified on your system in the past 60 minutes

find / -mmin 60 -type f

Find all files larger than 20M

find / -type f -size +20M

Find duplicate files (based on MD5 hash)

find -type f -exec md5sum '{}' ';' | sort | uniq --all-repeated=separate -w 33

Change permission only for files

cd /var/www/site && find . -type f -exec chmod 766 {} \;
cd /var/www/site && find . -type f -exec chmod 664 {} +

Change permission only for directories

cd /var/www/site && find . -type d -exec chmod g+x {} \;
cd /var/www/site && find . -type d -exec chmod g+rwx {} +

Find files and directories for specific user/group

# User:
find . -user <username> -print
find /etc -type f -user <username> -name "*.conf"

# Group:
find /opt -group <group>
find /etc -type f -group <group> -iname "*.conf"

Find files and directories for all without specific user/group

# User:
find . \! -user <username> -print

# Group:
find . \! -group <group>

Looking for files/directories that only have certain permission

# User
find . -user <username> -perm -u+rw # -rw-r--r--
find /home -user $(whoami) -perm 777 # -rwxrwxrwx

# Group:
find /home -type d -group <group> -perm 755 # -rwxr-xr-x

Delete older files than 60 days

find . -type f -mtime +60 -delete

Recursively remove all empty sub-directories from a directory

find . -depth  -type d  -empty -exec rmdir {} \;

How to find all hard links to a file

find </path/to/dir> -xdev -samefile filename

Recursively find the latest modified files

find . -type f -exec stat --format '%Y :%y %n' "{}" \; | sort -nr | cut -d: -f2- | head

Recursively find/replace of a string with sed

find . -not -path '*/\.git*' -type f -print0 | xargs -0 sed -i 's/foo/bar/g'

Recursively find/replace of a string in directories and file names

find . -depth -name '*test*' -execdir bash -c 'mv -v "$1" "${1//foo/bar}"' _ {} \;

Recursively find suid executables

find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -la {} \;

Tool: [top](https://en.wikipedia.org/wiki/Top_(software))

Use top to monitor only all processes with the specific string

top -p $(pgrep -d , <str>)

• <str> - process containing string (eg. nginx, worker)

Tool: vmstat

Show current system utilization (fields in kilobytes)

vmstat 2 20 -t -w

• 2 - number of times with a defined time interval (delay)

• 20 - each execution of the command (count)

• -t - show timestamp

• -w - wide output

• -S M - output of the fields in megabytes instead of kilobytes

Show current system utilization will get refreshed every 5 seconds

vmstat 5 -w

Display report a summary of disk operations

vmstat -D

Display report of event counters and memory stats

vmstat -s

Display report about kernel objects stored in slab layer cache

vmstat -m

Tool: iostat

Show information about the CPU usage, and I/O statistics about all the partitions

iostat 2 10 -t -m

• 2 - number of times with a defined time interval (delay)

• 10 - each execution of the command (count)

• -t - show timestamp

• -m - fields in megabytes (-k - in kilobytes, default)

Show information only about the CPU utilization

iostat 2 10 -t -m -c

Show information only about the disk utilization

iostat 2 10 -t -m -d

Show information only about the LVM utilization

iostat -N

Tool: strace

Track with child processes

# 1)
strace -f -p $(pidof glusterfsd)

# 2)
strace -f $(pidof php-fpm | sed 's/\([0-9]*\)/\-p \1/g')

Track process with 30 seconds limit

timeout 30 strace $(< /var/run/zabbix/zabbix_agentd.pid)

Track processes and redirect output to a file

ps auxw | grep '[a]pache' | awk '{print " -p " $2}' | \
xargs strace -o /tmp/strace-apache-proc.out

Track with print time spent in each syscall and limit length of print strings

ps auxw | grep '[i]init_policy' | awk '{print " -p " $2}' | \
xargs strace -f -e trace=network -T -s 10000

Track the open request of a network port

strace -f -e trace=bind nc -l 80

Track the open request of a network port (show TCP/UDP)

strace -f -e trace=network nc -lu 80

Tool: [kill](https://en.wikipedia.org/wiki/Kill_(command))

Kill a process running on port

kill -9 $(lsof -i :<port> | awk '{l=$2} END {print l}')

Tool: diff

Compare two directory trees

diff <(cd directory1 && find | sort) <(cd directory2 && find | sort)

Compare output of two commands

diff <(cat /etc/passwd) <(cut -f2 /etc/passwd)

Tool: vimdiff

Highlight the exact differences, based on characters and words

vimdiff file1 file2

Compare two JSON files

vimdiff <(jq -S . A.json) <(jq -S . B.json)

Compare Hex dump

d(){ vimdiff <(f $1) <(f $2);};f(){ hexdump -C $1|cut -d' ' -f3-|tr -s ' ';}; d ~/bin1 ~/bin2

diffchar

Save diffchar @ ~/.vim/plugins

Click F7 to switch between diff modes

Usefull vimdiff commands:

• qa to exit all windows

• :vertical resize 70 to resize window

• set window width Ctrl+W [N columns]+(Shift+)<\>

Tool: [tail](https://en.wikipedia.org/wiki/Tail_(Unix))

Annotate tail -f with timestamps

tail -f file | while read ; do echo "$(date +%T.%N) $REPLY" ; done

Analyse an Apache access log for the most common IP addresses

tail -10000 access_log | awk '{print $1}' | sort | uniq -c | sort -n | tail

Analyse web server log and show only 5xx http codes

tail -n 100 -f /path/to/logfile | grep "HTTP/[1-2].[0-1]\" [5]"

Tool: [tar](https://en.wikipedia.org/wiki/Tar_(computing))

System backup with exclude specific directories

cd /
tar -czvpf /mnt/system$(date +%d%m%Y%s).tgz --directory=/ \
--exclude=proc/* --exclude=sys/* --exclude=dev/* --exclude=mnt/* .

System backup with exclude specific directories (pigz)

cd /
tar cvpf /backup/snapshot-$(date +%d%m%Y%s).tgz --directory=/ \
--exclude=proc/* --exclude=sys/* --exclude=dev/* \
--exclude=mnt/* --exclude=tmp/* --use-compress-program=pigz .

Tool: [dump](https://en.wikipedia.org/wiki/Dump_(program))

System backup to file

dump -y -u -f /backup/system$(date +%d%m%Y%s).lzo /

Restore system from lzo file

cd /
restore -rf /backup/system$(date +%d%m%Y%s).lzo

Tool: cpulimit

Limit the cpu usage of a process

cpulimit -p pid -l 50

Tool: pwdx

Show current working directory of a process

pwdx <pid>

Tool: taskset

Start a command on only one CPU core

taskset -c 0 <command>

Tool: [tr](https://en.wikipedia.org/wiki/Tr_(Unix))

Show directories in the PATH, one per line

tr : '\n' <<<$PATH

Tool: chmod

Remove executable bit from all files in the current directory

chmod -R -x+X *

Restore permission for /bin/chmod

# 1:
cp /bin/ls chmod.01
cp /bin/chmod chmod.01
./chmod.01 700 file

# 2:
/bin/busybox chmod 0700 /bin/chmod

# 3:
setfacl --set u::rwx,g::---,o::--- /bin/chmod

Tool: [who](https://en.wikipedia.org/wiki/Who_(Unix))

Find last reboot time

who -b

Detect a user sudo-su'd into the current shell

[[ $(who -m | awk '{ print $1 }') == $(whoami) ]] || echo "You are su-ed to $(whoami)"

Tool: last

Was the last reboot a panic?

(last -x -f $(ls -1t /var/log/wtmp* | head -2 | tail -1); last -x -f /var/log/wtmp) | \
grep -A1 reboot | head -2 | grep -q shutdown && echo "Expected reboot" || echo "Panic reboot"

Tool: screen

Start screen in detached mode

screen -d -m <command>

Attach to an existing screen session

screen -r -d <pid>

Tool: [script](https://en.wikipedia.org/wiki/Script_(Unix))

Record and replay terminal session

### Record session
# 1)
script -t 2>~/session.time -a ~/session.log

# 2)
script --timing=session.time session.log

### Replay session
scriptreplay --timing=session.time session.log

Tool: du

Show 20 biggest directories with 'K M G'

du | \
sort -r -n | \
awk '{split("K M G",v); s=1; while($1>1024){$1/=1024; s++} print int($1)" "v[s]"\t"$2}' | \
head -n 20

Tool: inotifywait

Init tool everytime a file in a directory is modified

while true ; do inotifywait -r -e MODIFY dir/ && ls dir/ ; done;

Tool: openssl

Testing connection to the remote host

echo | openssl s_client -connect google.com:443 -showcerts

Testing connection to the remote host (debug mode)

echo | openssl s_client -connect google.com:443 -showcerts -tlsextdebug -status

Testing connection to the remote host (with SNI support)

echo | openssl s_client -showcerts -servername google.com -connect google.com:443

Testing connection to the remote host with specific ssl version

openssl s_client -tls1_2 -connect google.com:443

Testing connection to the remote host with specific ssl cipher

openssl s_client -cipher 'AES128-SHA' -connect google.com:443

Verify 0-RTT

_host="example.com"

cat > req.in << __EOF__
HEAD / HTTP/1.1
Host: $_host
Connection: close
__EOF__

openssl s_client -connect ${_host}:443 -tls1_3 -sess_out session.pem -ign_eof < req.in
openssl s_client -connect ${_host}:443 -tls1_3 -sess_in session.pem -early_data req.in

Generate private key without passphrase

# _len: 2048, 4096
( _fd="private.key" ; _len="2048" ; \
openssl genrsa -out ${_fd} ${_len} )

Generate private key with passphrase

# _ciph: des3, aes128, aes256
# _len: 2048, 4096
( _ciph="aes128" ; _fd="private.key" ; _len="2048" ; \
openssl genrsa -${_ciph} -out ${_fd} ${_len} )

Remove passphrase from private key

( _fd="private.key" ; _fd_unp="private_unp.key" ; \
openssl rsa -in ${_fd} -out ${_fd_unp} )

Encrypt existing private key with a passphrase

# _ciph: des3, aes128, aes256
( _ciph="aes128" ; _fd="private.key" ; _fd_pass="private_pass.key" ; \
openssl rsa -${_ciph} -in ${_fd} -out ${_fd_pass}

Check private key

( _fd="private.key" ; \
openssl rsa -check -in ${_fd} )

Get public key from private key

( _fd="private.key" ; _fd_pub="public.key" ; \
openssl rsa -pubout -in ${_fd} -out ${_fd_pub} )

Generate private key and CSR

( _fd="private.key" ; _fd_csr="request.csr" ; _len="2048" ; \
openssl req -out ${_fd_csr} -new -newkey rsa:${_len} -nodes -keyout ${_fd} )

Generate CSR

( _fd="private.key" ; _fd_csr="request.csr" ; \
openssl req -out ${_fd_csr} -new -key ${_fd} )

Generate CSR (metadata from existing certificate)

Where private.key is the existing private key. As you can see you do not generate this CSR from your certificate (public key). Also you do not generate the "same" CSR, just a new one to request a new certificate.

( _fd="private.key" ; _fd_csr="request.csr" ; _fd_crt="cert.crt" ; \
openssl x509 -x509toreq -in ${_fd_crt} -out ${_fd_csr} -signkey ${_fd} )

Generate CSR with -config param

( _fd="private.key" ; _fd_csr="request.csr" ; \
openssl req -new -sha256 -key ${_fd} -out ${_fd_csr} \
-config <(
cat << __EOF__
[req]
default_bits        = 2048
default_md          = sha256
prompt              = no
distinguished_name  = dn
req_extensions      = req_ext

[ dn ]
C   = "<two-letter ISO abbreviation for your country>"
ST  = "<state or province where your organisation is legally located>"
L   = "<city where your organisation is legally located>"
O   = "<legal name of your organisation>"
OU  = "<section of the organisation>"
CN  = "<fully qualified domain name>"

[ req_ext ]
subjectAltName = @alt_names

[ alt_names ]
DNS.1 = <fully qualified domain name>
DNS.2 = <next domain>
DNS.3 = <next domain>
__EOF__
))

Other values in [ dn ]:

countryName            = "DE"                     # C=
stateOrProvinceName    = "Hessen"                 # ST=
localityName           = "Keller"                 # L=
postalCode             = "424242"                 # L/postalcode=
postalAddress          = "Keller"                 # L/postaladdress=
streetAddress          = "Crater 1621"            # L/street=
organizationName       = "apfelboymschule"        # O=
organizationalUnitName = "IT Department"          # OU=
commonName             = "example.com"            # CN=
emailAddress           = "[email protected]"  # CN/emailAddress=

Example of oids (you'll probably also have to make OpenSSL know about the new fields required for EV by adding the following under [new_oids]):

[req]
...
oid_section         = new_oids

[ new_oids ]
postalCode = 2.5.4.17
streetAddress = 2.5.4.9

For more information please look at these great explanations:

• RFC 5280

• How to create multidomain certificates using config files

• Generate a multi domains certificate using config files

• Your OpenSSL CSR command is out of date

• OpenSSL example configuration file

List available EC curves

openssl ecparam -list_curves

Print ECDSA private and public keys

( _fd="private.key" ; \
openssl ec -in ${_fd} -noout -text )

# For x25519 only extracting public key
( _fd="private.key" ; _fd_pub="public.key" ; \
openssl pkey -in ${_fd} -pubout -out ${_fd_pub} )

Generate ECDSA private key

# _curve: prime256v1, secp521r1, secp384r1
( _fd="private.key" ; _curve="prime256v1" ; \
openssl ecparam -out ${_fd} -name ${_curve} -genkey )

# _curve: X25519
( _fd="private.key" ; _curve="x25519" ; \
openssl genpkey -algorithm ${_curve} -out ${_fd} )

Generate private key and CSR (ECC)

# _curve: prime256v1, secp521r1, secp384r1
( _fd="domain.com.key" ; _fd_csr="domain.com.csr" ; _curve="prime256v1" ; \
openssl ecparam -out ${_fd} -name ${_curve} -genkey ; \
openssl req -new -key ${_fd} -out ${_fd_csr} -sha256 )

Generate self-signed certificate

# _len: 2048, 4096
( _fd="domain.key" ; _fd_out="domain.crt" ; _len="2048" ; _days="365" ; \
openssl req -newkey rsa:${_len} -nodes \
-keyout ${_fd} -x509 -days ${_days} -out ${_fd_out} )

Generate self-signed certificate from existing private key

# _len: 2048, 4096
( _fd="domain.key" ; _fd_out="domain.crt" ; _days="365" ; \
openssl req -key ${_fd} -nodes \
-x509 -days ${_days} -out ${_fd_out} )

Generate self-signed certificate from existing private key and csr

# _len: 2048, 4096
( _fd="domain.key" ; _fd_csr="domain.csr" ; _fd_out="domain.crt" ; _days="365" ; \
openssl x509 -signkey ${_fd} -nodes \
-in ${_fd_csr} -req -days ${_days} -out ${_fd_out} )

Generate DH public parameters

( _dh_size="2048" ; \
openssl dhparam -out /etc/nginx/ssl/dhparam_${_dh_size}.pem "$_dh_size" )

Display DH public parameters

openssl pkeyparam -in dhparam.pem -text

Extract private key from pfx

( _fd_pfx="cert.pfx" ; _fd_key="key.pem" ; \
openssl pkcs12 -in ${_fd_pfx} -nocerts -nodes -out ${_fd_key} )

Extract private key and certs from pfx

( _fd_pfx="cert.pfx" ; _fd_pem="key_certs.pem" ; \
openssl pkcs12 -in ${_fd_pfx} -nodes -out ${_fd_pem} )

Extract certs from p7b

# PKCS#7 file doesn't include private keys.
( _fd_p7b="cert.p7b" ; _fd_pem="cert.pem" ; \
openssl pkcs7 -inform DER -outform PEM -in ${_fd_p7b} -print_certs > ${_fd_pem})
# or:
openssl pkcs7 -print_certs -in -in ${_fd_p7b} -out ${_fd_pem})

Convert DER to PEM

( _fd_der="cert.crt" ; _fd_pem="cert.pem" ; \
openssl x509 -in ${_fd_der} -inform der -outform pem -out ${_fd_pem} )

Convert PEM to DER

( _fd_der="cert.crt" ; _fd_pem="cert.pem" ; \
openssl x509 -in ${_fd_pem} -outform der -out ${_fd_der} )

Verification of the private key

( _fd="private.key" ; \
openssl rsa -noout -text -in ${_fd} )

Verification of the public key

# 1)
( _fd="public.key" ; \
openssl pkey -noout -text -pubin -in ${_fd} )

# 2)
( _fd="private.key" ; \
openssl rsa -inform PEM -noout -in ${_fd} &> /dev/null ; \
if [ $? = 0 ] ; then echo -en "OK\n" ; fi )

Verification of the certificate

( _fd="certificate.crt" ; # format: pem, cer, crt \
openssl x509 -noout -text -in ${_fd} )

Verification of the CSR

( _fd_csr="request.csr" ; \
openssl req -text -noout -in ${_fd_csr} )

Check the private key and the certificate are match

(openssl rsa -noout -modulus -in private.key | openssl md5 ; \
openssl x509 -noout -modulus -in certificate.crt | openssl md5) | uniq

Check the private key and the CSR are match

(openssl rsa -noout -modulus -in private.key | openssl md5 ; \
openssl req -noout -modulus -in request.csr | openssl md5) | uniq

Tool: secure-delete

Secure delete with shred

shred -vfuz -n 10 file
shred --verbose --random-source=/dev/urandom -n 1 /dev/sda

Secure delete with scrub

scrub -p dod /dev/sda
scrub -p dod -r file

Secure delete with badblocks

badblocks -s -w -t random -v /dev/sda
badblocks -c 10240 -s -w -t random -v /dev/sda

Secure delete with secure-delete

srm -vz /tmp/file
sfill -vz /local
sdmem -v
swapoff /dev/sda5 && sswap -vz /dev/sda5

Tool: [dd](https://en.wikipedia.org/wiki/Dd_(Unix))

Show dd status every so often

dd <dd_params> status=progress
watch --interval 5 killall -USR1 dd

Redirect output to a file with dd

echo "string" | dd of=filename

Tool: gpg

Export public key

gpg --export --armor "<username>" > username.pkey

• --export - export all keys from all keyrings or specific key

• -a|--armor - create ASCII armored output

Encrypt file

gpg -e -r "<username>" dump.sql

• -e|--encrypt - encrypt data

• -r|--recipient - encrypt for specific

Decrypt file

gpg -o dump.sql -d dump.sql.gpg

• -o|--output - use as output file

• -d|--decrypt - decrypt data (default)

Search recipient

gpg --keyserver hkp://keyserver.ubuntu.com --search-keys "<username>"

• --keyserver - set specific key server

• --search-keys - search for keys on a key server

List all of the packets in an encrypted file

gpg --batch --list-packets archive.gpg
gpg2 --batch --list-packets archive.gpg

Tool: system-other

Reboot system from init

exec /sbin/init 6

Init system from single user mode

exec /sbin/init

Show current working directory of a process

readlink -f /proc/<PID>/cwd

Show actual pathname of the executed command

readlink -f /proc/<PID>/exe

Tool: curl

curl -Iks https://www.google.com

• -I - show response headers only

• -k - insecure connection when using ssl

• -s - silent mode (not display body)

curl -Iks --location -X GET -A "x-agent" https://www.google.com

• --location - follow redirects

• -X - set method

• -A - set user-agent

curl -Iks --location -X GET -A "x-agent" --proxy http://127.0.0.1:16379 https://www.google.com

• --proxy [socks5://|http://] - set proxy server

curl -o file.pdf -C - https://example.com/Aiju2goo0Ja2.pdf

• -o - write output to file

• -C - resume the transfer

Find your external IP address (external services)

curl ipinfo.io
curl ipinfo.io/ip
curl icanhazip.com
curl ifconfig.me/ip ; echo

Repeat URL request

# URL sequence substitution with a dummy query string:
curl -ks https://example.com/?[1-20]

# With shell 'for' loop:
for i in {1..20} ; do curl -ks https://example.com/ ; done

Check DNS and HTTP trace with headers for specific domains

### Set domains and external dns servers.
_domain_list=(google.com) ; _dns_list=("8.8.8.8" "1.1.1.1")

for _domain in "${_domain_list[@]}" ; do

  printf '=%.0s' {1..48}

  echo

  printf "[\\e[1;32m+\\e[m] resolve: %s\\n" "$_domain"

  for _dns in "${_dns_list[@]}" ; do

    # Resolve domain.
    host "${_domain}" "${_dns}"

    echo

  done

  for _proto in http https ; do

    printf "[\\e[1;32m+\\e[m] trace + headers: %s://%s\\n" "$_proto" "$_domain"

    # Get trace and http headers.
    curl -Iks -A "x-agent" --location "${_proto}://${_domain}"

    echo

  done

done

unset _domain_list _dns_list

Tool: httpie

http -p Hh https://www.google.com

• -p - print request and response headers

  • H - request headers

  • B - request body

  • h - response headers

  • b - response body

http -p Hh https://www.google.com --follow --verify no

• -F, --follow - follow redirects

• --verify no - skip SSL verification

http -p Hh https://www.google.com --follow --verify no \
--proxy http:http://127.0.0.1:16379

• --proxy [http:] - set proxy server

Tool: ssh

Escape Sequence

# Supported escape sequences:
~.  - terminate connection (and any multiplexed sessions)
~B  - send a BREAK to the remote system
~C  - open a command line
~R  - Request rekey (SSH protocol 2 only)
~^Z - suspend ssh
~#  - list forwarded connections
~&  - background ssh (when waiting for connections to terminate)
~?  - this message
~~  - send the escape character by typing it twice

Compare a remote file with a local file

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

SSH connection through host in the middle

ssh -t reachable_host ssh unreachable_host

Run command over SSH on remote host

cat > cmd.txt << __EOF__
cat /etc/hosts
__EOF__

ssh host -l user $(<cmd.txt)

Get public key from private key

ssh-keygen -y -f ~/.ssh/id_rsa

Get all fingerprints

ssh-keygen -l -f .ssh/known_hosts

SSH authentication with user password

ssh -o PreferredAuthentications=password -o PubkeyAuthentication=no user@remote_host

SSH authentication with publickey

ssh -o PreferredAuthentications=publickey -o PubkeyAuthentication=yes -i id_rsa user@remote_host

Simple recording SSH session

function _ssh_sesslog() {

  _sesdir="<path/to/session/logs>"

  mkdir -p "${_sesdir}" && \
  ssh $@ 2>&1 | tee -a "${_sesdir}/$(date +%Y%m%d).log"

}

# Alias:
alias ssh='_ssh_sesslog'

Using Keychain for SSH logins

### Delete all of ssh-agent's keys.
function _scl() {

  /usr/bin/keychain --clear

}

### Add key to keychain.
function _scg() {

  /usr/bin/keychain /path/to/private-key
  source "$HOME/.keychain/$HOSTNAME-sh"

}

SSH login without processing any login scripts

ssh -tt user@host bash

SSH local port forwarding

Example 1:

# Forwarding our local 2250 port to nmap.org:443 from localhost through localhost
host1> ssh -L 2250:nmap.org:443 localhost

# Connect to the service:
host1> curl -Iks --location -X GET https://localhost:2250

Example 2:

# Forwarding our local 9051 port to db.d.x:5432 from localhost through node.d.y
host1> ssh -nNT -L 9051:db.d.x:5432 node.d.y

# Connect to the service:
host1> psql -U db_user -d db_dev -p 9051 -h localhost

• -n - redirects stdin from /dev/null

• -N - do not execute a remote command

• -T - disable pseudo-terminal allocation

SSH remote port forwarding

# Forwarding our local 9051 port to db.d.x:5432 from host2 through node.d.y
host1> ssh -nNT -R 9051:db.d.x:5432 node.d.y

# Connect to the service:
host2> psql -U postgres -d postgres -p 8000 -h localhost

Tool: linux-dev

Testing remote connection to port

timeout 1 bash -c "</dev/<proto>/<host>/<port>" >/dev/null 2>&1 ; echo $?

• <proto - set protocol (tcp/udp)

• <host> - set remote host

• <port> - set destination port

Read and write to TCP or UDP sockets with common bash tools

exec 5<>/dev/tcp/<host>/<port>; cat <&5 & cat >&5; exec 5>&-

Tool: tcpdump

Filter incoming (on interface) traffic (specific )

tcpdump -ne -i eth0 -Q in host 192.168.252.1 and port 443

• -n - don't convert addresses (-nn will not resolve hostnames or ports)

• -e - print the link-level headers

• -i [iface|any] - set interface

• -Q|-D [in|out|inout] - choose send/receive direction (-D - for old tcpdump versions)

• host [ip|hostname] - set host, also [host not]

• [and|or] - set logic

• port [1-65535] - set port number, also [port not]

Filter incoming (on interface) traffic (specific ) and write to a file

tcpdump -ne -i eth0 -Q in host 192.168.252.1 and port 443 -c 5 -w tcpdump.pcap

• -c [num] - capture only num number of packets

• -w [filename] - write packets to file, -r [filename] - reading from file

Capture all ICMP packets

tcpdump -nei eth0 icmp

Check protocol used (TCP or UDP) for service

tcpdump -nei eth0 tcp port 22 -vv -X | egrep "TCP|UDP"

Display ASCII text (to parse the output using grep or other)

tcpdump -i eth0 -A -s0 port 443

Grab everything between two keywords

tcpdump -i eth0 port 80 -X | sed -n -e '/username/,/=ldap/ p'

Grab user and pass ever plain http

tcpdump -i eth0  port http -l -A | egrep -i \
'pass=|pwd=|log=|login=|user=|username=|pw=|passw=|passwd=|password=|pass:|user:|username:|password:|login:|pass |user ' \
--color=auto --line-buffered -B20

Extract HTTP User Agent from HTTP request header

tcpdump -ei eth0 -nn -A -s1500 -l | grep "User-Agent:"

Capture only HTTP GET and POST packets

tcpdump -ei eth0 -s 0 -A -vv \
'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x47455420' or 'tcp[((tcp[12:1] & 0xf0) >> 2):4] = 0x504f5354'

or simply:

tcpdump -ei eth0 -s 0 -v -n -l | egrep -i "POST /|GET /|Host:"

Rotate capture files

tcpdump -ei eth0 -w /tmp/capture-%H.pcap -G 3600 -C 200

• -G <num> - pcap will be created every <num> seconds

• -C <size> - close the current pcap and open a new one if is larger than <size>

Top hosts by packets

tcpdump -ei enp0s25 -nnn -t -c 200 | cut -f 1,2,3,4 -d '.' | sort | uniq -c | sort -nr | head -n 20

Excludes any RFC 1918 private address

tcpdump -nei eth0 'not (src net (10 or 172.16/12 or 192.168/16) and dst net (10 or 172.16/12 or 192.168/16))'

Tool: tcpick

Analyse packets in real-time

while true ; do tcpick -a -C -r dump.pcap ; sleep 2 ; clear ; done

Tool: ngrep

ngrep -d eth0 "www.domain.com" port 443

• -d [iface|any] - set interface

• [domain] - set hostname

• port [1-65535] - set port number

ngrep -d eth0 "www.domain.com" src host 10.240.20.2 and port 443

• (host [ip|hostname]) - filter by ip or hostname

• (port [1-65535]) - filter by port number

ngrep -d eth0 -qt -O ngrep.pcap "www.domain.com" port 443

• -q - quiet mode (only payloads)

• -t - added timestamps

• -O [filename] - save output to file, -I [filename] - reading from file

ngrep -d eth0 -qt 'HTTP' 'tcp'

• HTTP - show http headers

• tcp|udp - set protocol

• [src|dst] host [ip|hostname] - set direction for specific node

ngrep -l -q -d eth0 -i "User-Agent: curl*"

• -l - stdout line buffered

• -i - case-insensitive search

Tool: hping3

hping3 -V -p 80 -s 5050 <scan_type> www.google.com

• -V|--verbose - verbose mode

• -p|--destport - set destination port

• -s|--baseport - set source port

• <scan_type> - set scan type

  • -F|--fin - set FIN flag, port open if no reply

  • -S|--syn - set SYN flag

  • -P|--push - set PUSH flag

  • -A|--ack - set ACK flag (use when ping is blocked, RST response back if the port is open)

  • -U|--urg - set URG flag

  • -Y|--ymas - set Y unused flag (0x80 - nullscan), port open if no reply

  • -M 0 -UPF - set TCP sequence number and scan type (URG+PUSH+FIN), port open if no reply

hping3 -V -c 1 -1 -C 8 www.google.com

• -c [num] - packet count

• -1 - set ICMP mode

• -C|--icmptype [icmp-num] - set icmp type (default icmp-echo = 8)

hping3 -V -c 1000000 -d 120 -S -w 64 -p 80 --flood --rand-source <remote_host>

• --flood - sent packets as fast as possible (don't show replies)

• --rand-source - random source address mode

• -d --data - data size

• -w|--win - winsize (default 64)

Tool: nmap

Ping scans the network

nmap -sP 192.168.0.0/24

Show only open ports

nmap -F --open 192.168.0.0/24

Full TCP port scan using with service version detection

nmap -p 1-65535 -sV -sS -T4 192.168.0.0/24

Nmap scan and pass output to Nikto

nmap -p80,443 192.168.0.0/24 -oG - | nikto.pl -h -

Recon specific ip:service with Nmap NSE scripts stack

# Set variables:
_hosts="192.168.250.10"
_ports="80,443"

# Set Nmap NSE scripts stack:
_nmap_nse_scripts="+dns-brute,\
                   +http-auth-finder,\
                   +http-chrono,\
                   +http-cookie-flags,\
                   +http-cors,\
                   +http-cross-domain-policy,\
                   +http-csrf,\
                   +http-dombased-xss,\
                   +http-enum,\
                   +http-errors,\
                   +http-git,\
                   +http-grep,\
                   +http-internal-ip-disclosure,\
                   +http-jsonp-detection,\
                   +http-malware-host,\
                   +http-methods,\
                   +http-passwd,\
                   +http-phpself-xss,\
                   +http-php-version,\
                   +http-robots.txt,\
                   +http-sitemap-generator,\
                   +http-shellshock,\
                   +http-stored-xss,\
                   +http-title,\
                   +http-unsafe-output-escaping,\
                   +http-useragent-tester,\
                   +http-vhosts,\
                   +http-waf-detect,\
                   +http-waf-fingerprint,\
                   +http-xssed,\
                   +traceroute-geolocation.nse,\
                   +ssl-enum-ciphers,\
                   +whois-domain,\
                   +whois-ip"

# Set Nmap NSE script params:
_nmap_nse_scripts_args="dns-brute.domain=${_hosts},http-cross-domain-policy.domain-lookup=true,"
_nmap_nse_scripts_args+="http-waf-detect.aggro,http-waf-detect.detectBodyChanges,"
_nmap_nse_scripts_args+="http-waf-fingerprint.intensive=1"

# Perform scan:
nmap --script="$_nmap_nse_scripts" --script-args="$_nmap_nse_scripts_args" -p "$_ports" "$_hosts"

Tool: netcat

nc -kl 5000

• -l - listen for an incoming connection

• -k - listening after client has disconnected

• >filename.out - save receive data to file (optional)

nc 192.168.0.1 5051 < filename.in

• < filename.in - send data to remote host

nc -vz 10.240.30.3 5000

• -v - verbose output

• -z - scan for listening daemons

nc -vzu 10.240.30.3 1-65535

• -u - scan only udp ports

Transfer data file (archive)

server> nc -l 5000 | tar xzvfp -
client> tar czvfp - /path/to/dir | nc 10.240.30.3 5000

Launch remote shell

# 1)
server> nc -l 5000 -e /bin/bash
client> nc 10.240.30.3 5000

# 2)
server> rm -f /tmp/f; mkfifo /tmp/f
server> cat /tmp/f | /bin/bash -i 2>&1 | nc -l 127.0.0.1 5000 > /tmp/f
client> nc 10.240.30.3 5000

Simple file server

while true ; do nc -l 5000 | tar -xvf - ; done

Simple minimal HTTP Server

while true ; do nc -l -p 1500 -c 'echo -e "HTTP/1.1 200 OK\n\n $(date)"' ; done

Simple HTTP Server

Restarts web server after each request - remove while condition for only single connection.

cat > index.html << __EOF__
<!doctype html>
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
        <title></title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
    </head>
    <body>

    <p>

      Hello! It's a site.

    </p>

    </body>
</html>
__EOF__

server> while : ; do \
(echo -ne "HTTP/1.1 200 OK\r\nContent-Length: $(wc -c <index.html)\r\n\r\n" ; cat index.html;) | \
nc -l -p 5000 \
; done

• -p - port number

Simple HTTP Proxy (single connection)

#!/usr/bin/env bash

if [[ $# != 2 ]] ; then
  printf "%s\\n" \
         "usage: ./nc-proxy listen-port bk_host:bk_port"
fi

_listen_port="$1"
_bk_host=$(echo "$2" | cut -d ":" -f1)
_bk_port=$(echo "$2" | cut -d ":" -f2)

printf "  lport: %s\\nbk_host: %s\\nbk_port: %s\\n\\n" \
       "$_listen_port" "$_bk_host" "$_bk_port"

_tmp=$(mktemp -d)
_back="$_tmp/pipe.back"
_sent="$_tmp/pipe.sent"
_recv="$_tmp/pipe.recv"

trap 'rm -rf "$_tmp"' EXIT

mkfifo -m 0600 "$_back" "$_sent" "$_recv"

sed "s/^/=> /" <"$_sent" &
sed "s/^/<=  /" <"$_recv" &

nc -l -p "$_listen_port" <"$_back" | \
tee "$_sent" | \
nc "$_bk_host" "$_bk_port" | \
tee "$_recv" >"$_back"

server> chmod +x nc-proxy && ./nc-proxy 8080 192.168.252.10:8000
  lport: 8080
bk_host: 192.168.252.10
bk_port: 8000

client> http -p h 10.240.30.3:8080
HTTP/1.1 200 OK
Accept-Ranges: bytes
Cache-Control: max-age=31536000
Content-Length: 2748
Content-Type: text/html; charset=utf-8
Date: Sun, 01 Jul 2018 20:12:08 GMT
Last-Modified: Sun, 01 Apr 2018 21:53:37 GMT

Create a single-use TCP or UDP proxy

### TCP -> TCP
nc -l -p 2000 -c "nc [ip|hostname] 3000"

### TCP -> UDP
nc -l -p 2000 -c "nc -u [ip|hostname] 3000"

### UDP -> UDP
nc -l -u -p 2000 -c "nc -u [ip|hostname] 3000"

### UDP -> TCP
nc -l -u -p 2000 -c "nc [ip|hostname] 3000"

Tool: gnutls-cli

Testing connection to remote host (with SNI support)

gnutls-cli -p 443 google.com

Testing connection to remote host (without SNI support)

gnutls-cli --disable-sni -p 443 google.com

Tool: socat

Testing remote connection to port

socat - TCP4:10.240.30.3:22

• - - standard input (STDIO)

• TCP4:<params> - set tcp4 connection with specific params

  • [hostname|ip] - set hostname/ip

  • [1-65535] - set port number

Redirecting TCP-traffic to a UNIX domain socket under Linux

socat TCP-LISTEN:1234,bind=127.0.0.1,reuseaddr,fork,su=nobody,range=127.0.0.0/8 UNIX-CLIENT:/tmp/foo

• TCP-LISTEN:<params> - set tcp listen with specific params

  • [1-65535] - set port number

  • bind=[hostname|ip] - set bind hostname/ip

  • reuseaddr - allows other sockets to bind to an address

  • fork - keeps the parent process attempting to produce more connections

  • su=nobody - set user

  • range=[ip-range] - ip range

• UNIX-CLIENT:<params> - communicates with the specified peer socket

  • filename - define socket

Tool: p0f

Set iface in promiscuous mode and dump traffic to the log file

p0f -i enp0s25 -p -d -o /dump/enp0s25.log

• -i - listen on the specified interface

• -p - set interface in promiscuous mode

• -d - fork into background

• -o - output file

Tool: netstat

Graph # of connections for each hosts

netstat -an | awk '/ESTABLISHED/ { split($5,ip,":"); if (ip[1] !~ /^$/) print ip[1] }' | \
sort | uniq -c | awk '{ printf("%s\t%s\t",$2,$1) ; for (i = 0; i < $1; i++) {printf("*")}; print "" }'

Monitor open connections for specific port including listen, count and sort it per IP

watch "netstat -plan | grep :443 | awk {'print \$5'} | cut -d: -f 1 | sort | uniq -c | sort -nk 1"

Grab banners from local IPv4 listening ports

netstat -nlt | grep 'tcp ' | grep -Eo "[1-9][0-9]*" | xargs -I {} sh -c "echo "" | nc -v -n -w1 127.0.0.1 {}"

Tool: rsync

Rsync remote data as root using sudo

rsync --rsync-path 'sudo rsync' username@hostname:/path/to/dir/ /local/

Tool: [host](https://en.wikipedia.org/wiki/Host_(Unix))

Resolves the domain name (using external dns server)

host google.com 9.9.9.9

Checks the domain administrator (SOA record)

host -t soa google.com 9.9.9.9

Tool: [dig](https://en.wikipedia.org/wiki/Dig_(command))

Resolves the domain name (short output)

dig google.com +short

Lookup NS record for specific domain

dig @9.9.9.9 google.com NS

Query only answer section

dig google.com +nocomments +noquestion +noauthority +noadditional +nostats

Query ALL DNS Records

dig google.com ANY +noall +answer

DNS Reverse Look-up

dig -x 172.217.16.14 +short

Tool: certbot

Generate multidomain certificate

certbot certonly -d example.com -d www.example.com

Generate wildcard certificate

certbot certonly --manual --preferred-challenges=dns -d example.com -d *.example.com

Generate certificate with 4096 bit private key

certbot certonly -d example.com -d www.example.com --rsa-key-size 4096

Tool: network-other

Get all subnets for specific AS (Autonomous system)

AS="AS32934"
whois -h whois.radb.net -- "-i origin ${AS}" | \
grep "^route:" | \
cut -d ":" -f2 | \
sed -e 's/^[ \t]//' | \
sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 | \
cut -d ":" -f2 | \
sed -e 's/^[ \t]/allow /' | \
sed 's/$/;/' | \
sed 's/allow  */subnet -> /g'

Resolves domain name from dns.google.com with curl and jq

_dname="google.com" ; curl -s "https://dns.google.com/resolve?name=${_dname}&type=A" | jq .

Tool: git

Log alias for a decent view of your repo

# 1)
git log --oneline --decorate --graph --all

# 2)
git log --graph \
--pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' \
--abbrev-commit

Tool: python

Static HTTP web server

# Python 3.x
python3 -m http.server 8000 --bind 127.0.0.1

# Python 2.x
python -m SimpleHTTPServer 8000

Static HTTP web server with SSL support

# Python 3.x
from http.server import HTTPServer, BaseHTTPRequestHandler
import ssl

httpd = HTTPServer(('localhost', 4443), BaseHTTPRequestHandler)

httpd.socket = ssl.wrap_socket (httpd.socket,
        keyfile="path/to/key.pem",
        certfile='path/to/cert.pem', server_side=True)

httpd.serve_forever()

# Python 2.x
import BaseHTTPServer, SimpleHTTPServer
import ssl

httpd = BaseHTTPServer.HTTPServer(('localhost', 4443),
        SimpleHTTPServer.SimpleHTTPRequestHandler)

httpd.socket = ssl.wrap_socket (httpd.socket,
        keyfile="path/tp/key.pem",
        certfile='path/to/cert.pem', server_side=True)

httpd.serve_forever()

Encode base64

python -m base64 -e <<< "sample string"

Decode base64

python -m base64 -d <<< "dGhpcyBpcyBlbmNvZGVkCg=="

Tool: awk

Search for matching lines

# egrep foo
awk '/foo/' filename

Search non matching lines

# egrep -v foo
awk '!/foo/' filename

Print matching lines with numbers

# egrep -n foo
awk '/foo/{print FNR,$0}' filename

Print the last column

awk '{print $NF}' filename

Find all the lines longer than 80 characters

awk 'length($0)>80{print FNR,$0}' filename

Print only lines of less than 80 characters

awk 'length < 80 filename

Print double new lines a file

awk '1; { print "" }' filename

Print line numbers

awk '{ print FNR "\t" $0 }' filename
awk '{ printf("%5d : %s\n", NR, $0) }' filename   # in a fancy manner

Print line numbers for only non-blank lines

awk 'NF { $0=++a " :" $0 }; { print }' filename

Print the line and the next two (i=5) lines after the line matching regexp

awk '/foo/{i=5+1;}{if(i){i--; print;}}' filename

Print the lines starting at the line matching 'server {' until the line matching '}'

awk '/server {/,/}/' filename

Print multiple columns with separators

awk -F' ' '{print "ip:\t" $2 "\n port:\t" $3' filename

Remove empty lines

awk 'NF > 0' filename

# alternative:
awk NF filename

Delete trailing white space (spaces, tabs)

awk '{sub(/[ \t]*$/, "");print}' filename

Delete leading white space

awk '{sub(/^[ \t]+/, ""); print}' filename

Remove duplicate consecutive lines

# uniq
awk 'a !~ $0{print}; {a=$0}' filename

Remove duplicate entries in a file without sorting

awk '!x[$0]++' filename

Exclude multiple columns

awk '{$1=$3=""}1' filename

Substitute foo for bar on lines matching regexp

awk '/regexp/{gsub(/foo/, "bar")};{print}' filename

Add some characters at the beginning of matching lines

awk '/regexp/{sub(/^/, "++++"); print;next;}{print}' filename

Get the last hour of Apache logs

awk '/'$(date -d "1 hours ago" "+%d\\/%b\\/%Y:%H:%M")'/,/'$(date "+%d\\/%b\\/%Y:%H:%M")'/ { print $0 }' \
/var/log/httpd/access_log

Tool: sed

Print a specific line from a file

sed -n 10p /path/to/file

Remove a specific line from a file

sed -i 10d /path/to/file
# alternative (BSD): sed -i'' 10d /path/to/file

Remove a range of lines from a file

sed -i <file> -re '<start>,<end>d'

Replace newline(s) with a space

sed ':a;N;$!ba;s/\n/ /g' /path/to/file

# cross-platform compatible syntax:
sed -e ':a' -e 'N' -e '$!ba' -e 's/\n/ /g' /path/to/file

• :a create a label a

• N append the next line to the pattern space

• $! if not the last line, ba branch (go to) label a

• s substitute, /\n/ regex for new line, / / by a space, /g global match (as many times as it can)

Alternatives:

# perl version (sed-like speed):
perl -p -e 's/\n/ /' /path/to/file

# bash version (slow):
while read line ; do printf "%s" "$line " ; done < file

Delete string +N next lines

sed '/start/,+4d' /path/to/file

Tool: grep

Search for a "pattern" inside all files in the current directory

grep -rn "pattern"
grep -RnisI "pattern" *
fgrep "pattern" * -R

Show only for multiple patterns

grep 'INFO*'\''WARN' filename
grep 'INFO\|WARN' filename
grep -e INFO -e WARN filename
grep -E '(INFO|WARN)' filename
egrep "INFO|WARN" filename

Except multiple patterns

grep -vE '(error|critical|warning)' filename

Show data from file without comments

grep -v ^[[:space:]]*# filename

Show data from file without comments and new lines

egrep -v '#|^$' filename

Show strings with a dash/hyphen

grep -e -- filename
grep -- -- filename
grep "\-\-" filename

Remove blank lines from a file and save output to new file

grep . filename > newfilename

Tool: perl

Search and replace (in place)

perl -i -pe's/SEARCH/REPLACE/' filename

Edit of *.conf files changing all foo to bar (and backup original)

perl -p -i.orig -e 's/\bfoo\b/bar/g' *.conf

Prints the first 20 lines from *.conf files

perl -pe 'exit if $. > 20' *.conf

Search lines 10 to 20

perl -ne 'print if 10 .. 20' filename

Delete first 10 lines (and backup original)

perl -i.orig -ne 'print unless 1 .. 10' filename

Delete all but lines between foo and bar (and backup original)

perl -i.orig -ne 'print unless /^foo$/ .. /^bar$/' filename

Reduce multiple blank lines to a single line

perl -p -i -00pe0 filename

Convert tabs to spaces (1t = 2sp)

perl -p -i -e 's/\t/  /g' filename

Read input from a file and report number of lines and characters

perl -lne '$i++; $in += length($_); END { print "$i lines, $in characters"; }' filename

Shell functions  [TOC]

Table of Contents

• Domain resolve

• Get ASN

Domain resolve

# Dependencies:
#   - curl
#   - jq

function DomainResolve() {

  local _host="$1"

  local _curl_base="curl --request GET"
  local _timeout="15"

  _host_ip=$($_curl_base -ks -m "$_timeout" "https://dns.google.com/resolve?name=${_host}&type=A" | \
  jq '.Answer[0].data' | tr -d "\"" 2>/dev/null)

  if [[ -z "$_host_ip" ]] || [[ "$_host_ip" == "null" ]] ; then

    echo -en "Unsuccessful domain name resolution.\\n"

  else

    echo -en "$_host > $_host_ip\\n"

  fi

}

Example:

shell> DomainResolve nmap.org
nmap.org > 45.33.49.119

shell> DomainResolve nmap.org
Unsuccessful domain name resolution.

Get ASN

# Dependencies:
#   - curl

function GetASN() {

  local _ip="$1"

  local _curl_base="curl --request GET"
  local _timeout="15"

  _asn=$($_curl_base -ks -m "$_timeout" "http://ip-api.com/line/${_ip}?fields=as")

  _state=$(echo $?)

  if [[ -z "$_ip" ]] || [[ "$_ip" == "null" ]] || [[ "$_state" -ne 0 ]]; then

    echo -en "Unsuccessful ASN gathering.\\n"

  else

    echo -en "$_ip > $_asn\\n"

  fi

}

Example:

shell> GetASN 1.1.1.1
1.1.1.1 > AS13335 Cloudflare, Inc.

shell> GetASN 0.0.0.0
Unsuccessful ASN gathering.