Terminal

# Make the script files executable
chmod a+x scripts/*.sh

# recursively option -R or --recursive
chmod -R 755 /path/to/directory

# To change all the directories to 755 (drwxr-xr-x):
find /path/to/directory -type d -exec chmod 755 {} \;
# To change all the files to 644 (-rw-r--r--):
find /path/to/directory -type f -exec chmod 644 {} \;

# Use the xargs command to pass multiple entries at once
sudo find /path/to/directory -type d -print0 | xargs -0 sudo chmod 755
sudo find /path/to/directory -type f -print0 | xargs -0 sudo chmod 644

cat /etc/shells # List the included shells on the system
chsh -s /bin/bash # Change default terminal to bash
chsh -s /bin/zsh # Change default terminal to zsh

du -sh [--apparent-size] <dir> # the total (-s) size of the directory in (-h) human readable format
du -h --max-depth=1 <dir> # disk usage of the first-level subdirectories
sudo du -h <dir> | sort -rh | head -5 # print the 5 largest directories within the dir directory


# Exclude a certain directory
du --exclude=./relative/path/to/target/dir

#To exclude certain files, use `du --exclude "WILDCARD" <dir>`
du --exclude "*.txt" * # Excludes all .txt files from calculation
# This can be done using exclude-from option too:
ls *.txt >EXCLUDE.txt
ls *.odt >>EXCLUDE.txt
du --exclude-from EXCLUDE.txt

df -h

# List the content
tar -tf archive.tar.gz

# Extract the content
tar -xvf archive.tar.gz [-C /path/of/destination]
# option -x: extraction
#        -v: verbose

# Extract certain files or diretories
tar -xf archive.tar.gz /path/to/file1 /path/to/file2
tar -xf archive.tar.gz dir1 dir2

# Extract files of certian pattern
tar -xf archive.tar.gz --wildcards '*.jpg'

grep -rnw '/path/to/somewhere/' -e "pattern"
grep --include=\*.{c,h} -rnw '/path/to/somewhere/' -e "pattern"
grep --exclude=\*.o -rnw '/path/to/somewhere/' -e "pattern"
grep --exclude-dir={dir1,dir2,*.dst} -rnw '/path/to/search/' -e "pattern"
# output the line number only
grep -n '/path/to/somefile' -e "pattern" | cut -f1 -d:
# output the two words separated by the delimiter :
grep -n '/path/to/somefile' -e "pattern" | cut -f1,2 -d:
# loop over the returned result
for i in $(grep -n '/path/to/somefile' -e "pattern" | cut -f1 -d:); do 
    echo "$i"
done
# return only the first result
grep -n '/path/to/somefile' -e "pattern" | head -1

find="foo"
replace="bar"

# find $find and replace with $replace using sed 
# ending "/g" means globally replace all occurences
sed -i 's/$find/$replace/g' input.txt
# editing result saved to a new file
sed 's/$find/$replace/g' input.txt > output.txt

# ending "I" means case insensitive search
sed -i 's/word1/word2/gI' input

# you can change the delimiter to keep syntax simple
sed -i 's+word1+word2+g' input
sed -i 's_word1_word2_g' input

# only find word1 and replace it with word2 if line has a specific string such as FOO
sed -i -e '/FOO/s/word1/word2/' input.txt

# replace entire line 7 by line number
sed -i -e '7s/.*/line_replacement/' input.txt
# sed uses symbol $ as the address of the last line
sed -i -e '$s/.*/line_replacement/' input.txt

# insert a new line at line 3
sed -i "3inew line content" input.txt
# insert a new line at the line of the first matched pattern
sed -i "$(grep -n '<input-filepath>' -e 'pattern' | head -1 | cut -f1 -d:)inew line content" input.txt

# correct our md file
sed -i 's/% highlight terminal %}/% highlight bash %}/' "*.md"

# find the files with the name_pattern in all the folders below your directory
find /your/directory -iname <name_pattern> # *.jpg

# "-a" reserves file attributes, "-r" for recursive copy
cp -ar /source/. /dest/

# List the user processes of the port
sudo lsof -i -P -n | grep LISTEN
sudo lsof -i :<port-number>

sudo netstat -tulpn | grep LISTEN
sudo ss -tulpn | grep LISTEN
sudo nmap -sTU -O IP-address-Here
# Kill the process that occopying the port with its PID
sudo kill -9 <PID-occupying-the-port>

# Download file using curl
curl -L http://some.url --output some.file