cat -T | find | xargs -n 3 | uniq | chmod . -R | mkisofs | netstat -tnp | pkill

cat food 1> kitty "equal to>" cat food > kitty

less fex
#!/bin/bash
FILE=$1
if [ -f $FILE ]
then
echo File exists
else
echo Does not exists
fi

------

Remove blank lines

cat fex | tr -s '\n'

Show tabs

cat -T fex

List dirs

find . -type d

multiple criterions

find . \( -name "*file" -o -type d \)

Find all files access last day

find . -atime -1 -type f

Find files less than 2k

find . -size -2k

M – mb

G - Gb

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Delete files

find . -name "er*" –delete

Print files with permission 644

find . -perm 644

Cat all files

find . -name "*file" -print  -exec cat {} \;

it’s not possible to use multiple commands with –exec parameter, but we can write multiple commands in shell scripts

-exec ./commands.sh {} \;

xargs

$cat g | xargs

1 2 3 4 5 6 7 9 10 11 12

$ cat g | xargs -n 3

1 2 3

4 5 6

7 9 10

11 12

echo splitXsuplitXsplitXsplit | xargs -d X -n 2

split suplit

split split

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Find and delete all files

find . -type f -name "*.txt" -print | xargs rm –f

echo HELLO | tr 'A-z' 'a-z'

hello

echo Hello 123 world | tr -d '0-9'

Hello  world

------------

Verify md5 sum of particular file

md5sum filename > file_sum.md5
md5sum –c file_sum.md5

cat u

hello

hello

hello1

hello2

hello3

uniq -u u

hello1

hello2

hello3

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By setting the sticky bit, it restricts only the user owning it to delete the files even though group and others have sufficient permissions

How to set sticky bit

chmod +t newdir1/

set permissions 777 recurto all files and directories

chmod 777 . -R

To print the second line:

awk 'FNR == 2 {print}'

To print the second field:

awk '{print $2}'

To print the third field of the fifth line:

awk 'FNR == 5 {print $3}'

Create file with size 10Mbyte

dd if=/dev/zero of=bigfile bs=10M count=1

----------------

mkisofs is a command used to create ISO system

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List opened TCP ports and services

netstat -tnp

ubuntu2@ubuntu2:~$ sudo netstat -p | grep EST
tcp        0      0 ubuntu2.server.loca:ssh 192.168.154.1:50077     ESTABLISHED 7876/sshd: ubuntu2 
tcp        0      0 ubuntu2.server.lo:50237 bud02s24-in-f14.1:https ESTABLISHED 4339/firefox 

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pkill command is similar to the kill command but it accepts a process name instead of a process ID

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