Number of files
ls -l filename* | wc -l
Command to print directory structure
ls -R MY_FOLDER | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//──/g' -e 's/─/├/' -e '$s/├/└/'
List only directories
ls -l | grep '^d'
Count total number of files in particular directory with specific extension.
ls -lR /path/to/dir/*.jpg | wc -l
Max thread, we can use. or number CPU.
-Search multiple strings
grep '1\|2\|3' filename
-Number of lines with specific pattern search
grep -o 'STRING' filename | wc -l
SED
Replace values in file,
sed -i 's/old_string/new_string/' filename
With special character simple quotes
sed -i "s/old_string/'new_string'/g" filename
Add header string in the file.
sed -i '1s/^/addedtext\n/' filename
Add footer string in the file
echo "helloworld" | tee -a filename >/dev/null
Change extension filename in loop
for f in filename.txt;do mv $f $f.sql;done
Split larger files into smaller parts
-l number of lines
split -l 500000 filename
--bytes
K
M
G
Execute next the command on terminal example:
split --bytes=1G path/your_file.extension path/your_new_file.extension
Convert file UTF-8
iconv -f ISO-8859-1 -t UTF-8//TRANSLIT filein.txt > fileout.txt
Check special character on file
grep --color='auto' -P -n "[\x80-\xFF]" file.txt
Could not get lock /var/lib/dpkg/lock-frontend - open
Delete the lock file:
sudo rm /var/lib/apt/lists/lock
Delete the lock file in the cache directory
sudo rm /var/cache/apt/archives/lock
sudo rm /var/lib/dpkg/lock
Generate RSA private and public key
Private key:
openssl genrsa -out private.pem 2048
Public Key from RSA private key:
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!
Solution: run next command
ssh-keygen -R YOUR_IP