USO_v1

ADRESE IPV4 : ip -brief -4 address
MEMORIA LIBERA : free -h | head -2 | tail -1 | awk '{print $NF}'
? masina nu are adresa ip si te uiti la docker ?
sudo runuser -l red -c 'echo "I am $USER with uid $UID"'


ip a s
ip link
ip l
ssh student@8.8.8.8
scp -r username1@source_host:directory1/file1
username2@destination_host:directory2/file2

### Tar & Zip

tar cvf         # Add to archive
tar xvf         # Extract
tar tf          # Show contents

tar czvf        # Add to archive - compressed
tar xzvf        # Extract        - compressed (optional)
tar ztf         # Show contents  - compressed (optional)

zip filename.zip files      # Add to archive
zip -u filename.zip files   # Update archive
unzip filename.zip          # Extract
zip -sf                     # Show contents

*******************************************************************************
# Sort every process by memory, shows only user,uid,pid,%mem,%cpu,rss,cmd
ps -e -o user,uid,pid,%mem,%cpu,rss,cmd --sort=%mem

*******************************************************************************
dd if=/dev/urandom of=random bs=1M count=100    # File with random characters

dd if=/dev/zero of=zeros bs=1M count=69         # File with zeros

# 20 character long strings
echo $RANDOM | md5sum | head -c 20; echo;
tr -dc A-Za-z0-9 </dev/urandom | head -c 20 ; echo;
pwgen 20 1

*******************************************************************************
mkfs.ext3                                   # Make an ext3 partition
mount -t ext3 filename mount/location/here  # Mount filename to that location

*******************************************************************************
### System info

# Cpu info ------ procesoru
lscpu
cat /proc/meminfo

# Memory info
lsmem
cat /proc/cpuinfo
free

lshw        # Hardware info
lspci       # PCI devices info
lsusb       # USB info

*******************************************************************************
### Users

sudo adduser                            	# Longer more complex creation 
						  of user

sudo useradd -m gigel                   	# Create user with username

sudo useradd -m -d /home/gigel gigel -p passw   # Create user with spicific home
						  directory and pass
sudo groupadd namegroup				# Add a group for users


w               # Show who is logged on and what they are doing
who             # Show who is logged on
whoami          # Show the users name
id              # Shows id, uid, groups of current user, or a specific user
finger gigel    # Display information about a specific user (empty means all)
passwd gigel    # Change the password of a specific user (empty means current user)

su - gigel        # Switch to gigel user

userdel gigel   # Deletes gigel from the computer :(

*******************************************************************************
### Chmod and chown

#   Read    |   Write   |   Execute
#     4           2            1

chown +x / +r / +w      # Adds read, execute or write persision to everyone
chown 666               # Adds read and write to everyone

chown gigel tema-pclp   # Switches the ownership of tema-pclp to gigel
chown user:group file 1 # Switches the ownership of tema-pclp to user from the group group

*******************************************************************************
### SSH

ssh student@<ip-address>            # Connects to <ip-address> as student
ssh student@<ip-address> -p 2222    # Connects to <ip-address> as student on port 2222

scp /etc/passwd student@<ip-address>:~ # Copy passwd to the home directory of student
scp student@<ip-address>:/etc/passwd ~ # Copy passwd from remote to home directory

*******************************************************************************
### Encryption

# AES CBC type encryption with 256 bit key
openssl aes-256-cbc -in file.txt -out encrypted_file.enc -pass pass:"uso rules"

# Same but to decrypt
aes-256-cbc -d -in encrypted_file.enc -out decrypted_file.txt -pass pass:"uso rules"

# Hashing
md5sum
sha256sum

echo -n "apples" | md5sum

*******************************************************************************
### If

if condition1
then
...
elif codtion2
then
...
else
...
fi

*******************************************************************************
### For & while loops

# For loops from 1 to 10
for i in 1 2 3 4 5 6 7 8 9 10; do ... done
for ((i = 1; i <= 10; i++)); do ... done
for i in $(seq 1 10); do ... done
for i in $(seq -f "%02g" 1 10); do ... done

for f in *; do ... done                         # For loops for every file
for arg in $@; do ... done                      # For every argument

# For every user in passwd
for user in $(awk -F ":" '{print $1}' /etc/passwd);
do 
... 
done

# For every line in countries.csv
cat csv/countries.csv | while read line
do
...
done

# While loop
while condition
do
...
done

*******************************************************************************
### Split string

```bash

IFS=":"     # Your separator

# Get's every argument from /etc/passwd
cat /etc/passwd | while read user password uid gid gecos home shell
do
...
done

*******************************************************************************
### EXERCITII
1) cautarea din . a tuturor fisierelor ce contin search: find . -name "*search*"

2) afiseaza din /proc/meminfo liniile ce contin Mem: cat /proc/meminfo | grep "Mem"

3) cat & tac : printeaza & printeaza pe invers

4) primele 10 caractere: head -c 10

5) procese din sistem : CURS 3 PE OCW

6) printeaza cu tot cu nr de linii : grep -n

7) nu tine cont de litera mica si cea mare : grep -i

8) afiseaza liniile ce NU contin un pattern: grep -v

9) cauta recursiv: grep -r

10) codul cu care si a terminat executia o comanda : echo $?

11) /etc/passwd : info despre toti utilizatorii

12) extrage coloana N, pana la separatorul Q : cut -fN -d"Q"
					       awk -F' *' '{print $1,$2,$4}'

13) /dev/zero : generator de octeti cu val 0

14) /dev/urandom : generator de octeti caractere

15) inlocurire de cuvinte : sed "s/311CC/312CA/g" students.csv > students.out

16) sortare : 
	-t specifica separatorul
	-k specifica index-ul, sau cheia, coloanei dupa care vrem sa sortam intrarile
	n sortare numerică (implicit este alfabetica)
	-r sortare inversa (implicit crescator)

17) parametrii:
	$* este un string ($1, $2 … $n)
	$@ este o listă formată din argumentele scriptului
	$1, $2 … $n reprezintă fiecare parametru din script
	$0 este numele scriptului
	$# este numărul de argumente primite din linia de comandă

18) citire linii cu mai multi parametrii
#!/bin/bash
 
IFS=','
while read name group final_grade test_grade practical_grade; do
    echo "$name"
done < students.csv

19) backup de fisiere
#!/bin/bash
 
for file in $1/*
do
    if test -f $file; then
        stat --print="%a %F %n\n" $file
        cp $file $file.bkp
    fi
done

SAU

#!/bin/bash
 
for file in $(find /usr/share/pixmaps/ -type f -iname '*.jpg')
do
    echo $file
done

20) for i in $(seq -f "%02g" 1 3); do touch test-"$i".txt; done

21) TCP : sudo netstat -tulpn | grep LISTEN

22) utilizatorii aia care nu au shell  ul implicit /bin/bash :
		grep -v "/bin/bash"

23) convertire : inkscape --export-png=acl.png acl.svg

Caracter Efect în expresie regulată	
^	început de linie
$	sfârşit de linie
.	orice caracter
*	expresia anterioară de oricâte ori, posibil niciodată
+	expresia anterioară de oricâte ori, cel puţin o dată
[ajt]	orice caracter din setul de caractere a, j, t
[Aajt]	orice caracter mai puţin caracterele a, j, t
|	expresia anterioară sau expresia de după (una dintre cele două expresii)
?	expresia anterioară o dată sau niciodată



UTILIZATORI:
cat /etc/shells + sudo chmod --shell "adresa aia" utilizator
awk 'NR%2==1' file.txt

--- suma parametrilor
total=0

for i in $@; do
  (( total+=i ))
done

echo "The total is $total"

scb