linux

find
grep
sort & uniq
sed
awk
diff
Bash
- Ejemplo bucle For
- Ejemplo bucle While infinito
Shell-script
IPtables
Netplan

Find

Find searches a directory for files

find /tmp -type d -print

Find a filename

find / -name '*.txt'

Find type

find -type [TYPE]
  f: regular file
  d: directory
  l: symlink
  p: named pipe
  s: socket
  
find /tmp -type d,l

Find path and ipath

Search the full path, and ipath (case insensitive)

find / -path '*tmp*/*'

Find maxdepth

Only descend NUM levels when searching a directory.

find / -path '*tmp*/*' -maxdepth 2

Find -mtime

Files that were modified at most NUM days in the past.

find / -name '*.py' -mtime 2

Find -print

Action: print filename of files found.

find . -name '*.py' -mtime 0 -print
./test.py
./test3.py
./test2.py

find . -name '*.py' -mtime 0 -print0 
./test.py./test3.py./test2.py

find . -name '*.py' -mtime 0 -print0 | xargs -0
./test.py ./test3.py ./test2.py

Find -exec

Action: run COMMAND on every file found.

find . -name '*.py' -mtime 0 -exec ls -l '{}' \;
find . -name '*.py' -mtime 0 -exec cat '{}' \;

Find -delete

Action: delete all files found

find . -name '*.py' -mtime 0 -delete

Locate and updatedb

The locate command searches a adatabase of eery file on your system. Faster than find, but cant get out of date.

Updates the database:

$ sudo updatedb

grep

grep lets you search fiels for text

grep -i

Case insensitive.

$ grep -i Apple foo.txt 
apple

grep -e or egrep

Search regular expressions.

$ grep -e '^....$' foo.txt 
kiwi

grep -v

Invert match, find all lines that don't match.

$ grep -ve '^....$' foo.txt 
apple
banana
orange

grep -l

Only show the filenames of the files that matched.

$ grep -le '^....$' *.txt 
foo.txt

grep -o

Only print the matching part of the line (not the whole line).

$ grep 'kiwi' foo.txt 
kiwi
kiwi with orange

$ grep -o 'kiwi' foo.txt 
kiwi
kiwi

grep -A -B -C

Show context for your search.

Will show 1 line of context after a match, before a match, context.

$ grep -A 1 'banana' foo.txt 
banana
orange

$ grep -B 1 'banana' foo.txt 
apple
banana

$ grep -C 1 'banana' foo.txt 
apple
banana
orange

grep -F

Don't treat the match string as a regex.

grep -r

Recursive. Search all the files in a directory.

grep -a

Search binaries: threat binary data like it's text instead of ignoring it.

sort & uniq

sort sorts its input. The default sort is alphabetical.

$ sort foo.txt 
apple,10
banana,5
kiwi with orange,10000
kiwi,500
orange,1000

sort -n

Numeric sort on second column.

$ sort -n -t ',' -k 2 foo.txt 
banana,5
apple,10
kiwi,500
orange,1000
kiwi with orange,10000

sort -h

Human sort.

$ sort -h -t ',' -k 2 foo.txt 
banana,5
apple,10
kiwi,500
orange,1K
kiwi with orange,10K

Useful example:

$ du -sh * | sort -h

sort + uniq

Pipe something to sort | uniq and you'll get a deduplicated list of lines. sort -u does the same thing.

$ cat foo2.txt 
apple
banana
orange
apple
kiwi
orange
orange
kiwi
apple
orange

$ cat foo2.txt | sort | uniq
apple
banana
kiwi
orange

$ sort -u foo2.txt 
apple
banana
kiwi
orange

uniq -c counts each line it saw.

$ cat foo2.txt | sort | uniq -c
      3 apple
      1 banana
      2 kiwi
      4 orange

Get the top 10 most common lines in a file.

$ sort foo2.txt | uniq -c | sort -rn | tail -n 10
      4 orange
      3 apple
      2 kiwi
      1 banana

sed

sed is most often used for replacing text in a file.

sed replace

Replaces orange by lemon.

$ sed s/orange/lemon/g foo2.txt 
apple
banana
lemon
apple
kiwi
lemon
lemon
kiwi
apple
lemon

sed delete

Delete 5th line.

$sed 5d foo2.txt 
apple
banana
orange
apple
orange
orange
kiwi
apple
orange

Delete lines matching kiwi.

$ sed /kiwi/d foo2.txt 
apple
banana
orange
apple
orange
orange
apple
orange

sed print

Print line 5-8

$ cat -n foo2.txt 
     1	apple
     2	banana
     3	orange
     4	apple
     5	kiwi
     6	orange
     7	orange
     8	kiwi
     9	apple
    10	orange

$ sed -n 5,8p foo2.txt 
kiwi
orange
orange
kiwi

sed change in place

Change a file in place with -i.

$ sed -i s/orange/lemon/g foo2.txt 

$ cat foo2.txt 
apple
banana
lemon
apple
kiwi
lemon
lemon
kiwi
apple
lemon

$ sed -i s/lemon/orange/g foo2.txt 

$ cat foo2.txt 
apple
banana
orange
apple
kiwi
orange
orange
kiwi
apple
orange

sed changed lines

Only print changed lines.

$ sed -n s/orange/lemon/p foo2.txt
lemon
lemon
lemon
lemon

sed regex delimeter

Use this if your regex has a / in it.

$ sed s#orange#lemon#g foo2.txt
apple
banana
lemon
apple
kiwi
lemon
lemon
kiwi
apple
lemon

sed double space a file

Double space a file.

$ sed G foo2.txt 
apple

banana

orange

apple

kiwi

orange

orange

kiwi

apple

orange

sed append after

Added grape after banana.

$ sed '/banana/a grape' foo2.txt 
apple
banana
grape
orange
apple
kiwi
orange
orange
kiwi
apple
orange

sed insert on line

Inserted grape before banana.

$ sed '/banana/i grape' foo2.txt 
apple
grape
banana
orange
apple
kiwi
orange
orange
kiwi
apple
orange

Insert on line number 4 grape

$ sed '4i grape' foo2.txt 
apple
banana
orange
grape
apple
kiwi
orange
orange
kiwi
apple
orange

awk

awk is a tiny programming language for manipulating columns of data.

awk structure

Basic awk program structure. Do {action} on line matching CONDITION.

BEGIN { ... }
CONDITION {action}
CONDITION {action}
END { ... }

awk print

$ awk -F, '{ print $0 }' foo3.txt 
apple,10
banana,5
kiwi,500
orange,1000
apple,18
kiwi,10000

awk extract a column

Extract a column of text with awk, with column separator comma.

$ awk -F, '{ print $2 }' foo3.txt 
10
5
500
1000
18
10000

awk sum

sum the numbers in the 2nd column.

$ awk -F, '{ s+=$2 } END { print s }' foo3.txt 
11533

awk condition

Only sum numbers > 100.

$ awk -F, '$2 > 100 { s+=$2 } END { print s }' foo3.txt 
11500

Print lines where first column is longer than 4 characters. Implicit {print} as the action.

$ awk -F, 'length($1)>4' foo3.txt 
apple,10
banana,5
orange,1000

490 491

apple,18

Diff

Ejemplo visualización en columnas

diff -y fichero1.txt fichero2.txt

Ejemplo comparar sin diferenciar espacios en blanco ni tabuladores

diff -wEZB  fichero1.txt fichero2.txt

Ejemplo modo silencioso

Importa el resultado del commando diff result=0 EXIT OK, result=1 FAIL.

result=$(diff -q --ignore-matching-lines="ntp clock-period" fichero1.txt fichero2.txt)

Ejemplo ignorando lineas

Las líneas con contenido "ntp clock-period" son ignoradas.

diff --ignore-matching-lines="ntp clock-period" fichero1.txt fichero2.txt

Comandos utilies del diff

diff 
      --suppress-blank-empty     suppress space or tab before empty output lines
      -y, --side-by-side         output in two columns
      -w, --ignore-all-space     ignore all white space
      -B, --ignore-blank-lines   ignore changes where lines are all blank
      -i, --ignore-case          ignore case differences in file contents
      -E, --ignore-tab-expansion ignore changes due to tab expansion
      -q, --brief                report only when files differ
      --suppress-common-lines    do not output common lines

Bash

Ejemplo Bucle For

for i in $(ls -a); do echo "fichero ${i}"; done

Ejemplo Bucle While infinito

while [ true ]; do echo "hello world\n"; sleep 3; done

Shell-script

Inicio bash

#!/bin/bash

ECHO=$(which echo)
CAT=$(which cat)
NMAP=$(which nmap)
RM=$(which rm)
DIFF=$(which diff)
 ...

Function

function Usage () {
        ${ECHO} -e "SYNTAX ERROR: ${0} [opcion1|opcion2] <nombre>\n"
        exit 1
}

IF - ELIF - ELSE - FI

Verificamos los parametros si son nulos, y si primer parametro contiene valor correcto.

if [[ -z ${1} ]] || [[ -z ${2} ]] ; then
  Usage
elif [[ "${1}" != "opcion1" ]] && [[ "${1}" != "opcion2" ]] ; then
  Usage
else
	accion="${1}"
	nombre="${2}"
fi

Si fichero existe entonces lo borramos:

if [[ -f "${nombreFichero}" ]] ; then
  ${RM} ${nombreFichero}
fi

Petición parámetros

${ECHO} "Introduce un nombre:"
read -s nombre

Case

case $opcion in
  0)
    ${ECHO} -e "[CORRECTO];"
    ;;
  *)
    ${ECHO} -e "[INCORRECTO];"
    ;;
esac

IPtables

sudo apt-get install iptables-persistent netfilter-persistent

vi  /etc/iptables/rules.v4 
# Generated by iptables-save v1.6.1 on Thu Mar  5 11:22:52 2020
*filter
:INPUT DROP [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:LOGGING - [0:0]
-A INPUT -i lo -j ACCEPT
-A INPUT -d 127.0.0.0/8 ! -i lo -j REJECT --reject-with icmp-port-unreachable
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s 192.168.14.0/25 -p tcp -m tcp --dport 22 -m comment --comment "SSH" -j ACCEPT
-A INPUT -p icmp -m comment --comment "PING" -j ACCEPT
-A INPUT -j LOGGING
-A LOGGING -m limit --limit 2 \/min -j LOG --log-prefix "IPTables:DROP: "
-A LOGGING -j DROP
COMMIT
\# Completed on Thu Mar  5 11:22:52 2020

vi /etc/rsyslog.d/40-iptables.conf
:msg, regex , "iptables:" -/var/log/firewall.log
& ~

sudo /etc/init.d/rsyslog restart

Netplan

& Ejemplo fichero netplan:

vi /etc/netplan/99-netcfg.yaml 
network:
   version: 2
   renderer: networkd
   ethernets:
     ens192:
       dhcp4: no
       dhcp6: no
       addresses:
         - 192.168.1.100/24
       gateway4: 192.168.1.1
       nameservers:
         addresses:
           - 9.9.9.9
           - 8.8.8.8 
      
netplan apply

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