Quick review for commands
Contents
Command Information
man chmod # Display page manual of a command
man -f|--whatis chmod # Display short description about a command
man -k|--apropos permission # Display all related commands from a specific keyword
chmod --help # Display usage options of a commandCommand History
history # View all previous commands
history | grep saman # View the commands using a specific word
history | grep -E|--extended-regexp -i|--ignore-case 'saman1|saman2|saman3' # View the commands using more than 1 specific word(case sensitive)
history | head -n|--lines 3 # View the first 3 executed commands
history 3 # View the last 3 executed commands
history -d 99 # Clear a command from a specific line
history -c # Clears all history commands
!! # Run the last command executed
touch saman.sh # <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<┐
chmod +x !$ # !$ is the last argument of the last command i.e. saman.sh <<<<┘Navigating Directories
pwd # Print current directory path
ls # List directories
ls -a|--all # List directories including hidden
ls -l # List directories in long form
ls -l -h|--human-readable # List directories in long form with human readable sizes
ls -t # List directories by modification time, newest first
stat saman.txt # List size, created and modified timestamps for a file
stat saman # List size, created and modified timestamps for a directory
tree # List directory and file tree
tree -a # List directory and file tree including hidden
tree -d # List directory tree
cd saman # Go to saman sub-directory
cd # Go to home directory
cd ~ # Go to home directory
cd - # Go to the previously chosen directory
pushd saman # Go to saman sub-directory and add previous directory to stack
popd # Go back to directory in stack saved by `pushd`Creating Directories
mkdir saman # Create a directory
mkdir saman bar # Create multiple directories
mkdir -p|--parents saman/bar # Create nested directory
mkdir -p|--parents {saman,bar}/baz # Create multiple nested directories
mktemp -d|--directory # Create a temporary directoryMoving Directories
cp -R|--recursive saman bar # Copy directory
mv saman bar # Move directory
rsync -z|--compress -v|--verbose /saman /bar # Copy directory, overwrites destination
rsync --ignore-existing -a|--archive -z|--compress -v|--verbose /saman /bar # Copy directory, without overwriting destination
rsync -avz /saman username@hostname:/bar # Copy local directory to remote directory
rsync -avz username@hostname:/saman /bar # Copy remote directory to local directoryDeleting Directories
rmdir saman # Delete non-empty directory
rm -r|--recursive saman # Delete directory including contents
rm -r|--recursive -f|--force saman # Delete directory including contents, ignore nonexistent files and never promptCreating Files
touch saman.txt # Create file or update existing files modified timestamp
touch saman.txt bar.txt # Create multiple files
touch {saman,bar}.txt # Create multiple files
touch test{1..3} # Create test1, test2 and test3 files
touch test{a..c} # Create testa, testb and testc files
mktemp # Create a temporary fileStandard Output, Standard Error and Standard Input
echo "saman" > bar.txt # Overwrite file with content
echo "saman" >> bar.txt # Append to file with content
ls exists 1> stdout.txt # Redirect the standard output to a file
ls noexist 2> stderror.txt # Redirect the standard error output to a file
ls > out.txt 2>&1 # Redirect standard output and error to a file
ls > /dev/null # Discard standard output and error
read saman # Read from standard input and write to the variable samanMoving Files
cp saman.txt bar.txt # Copy file
mv saman.txt bar.txt # Move file
rsync -z|--compress -v|--verbose /saman.txt /bar # Copy file quickly if not changed
rsync -z|--compress -v|--verbose /saman.txt /bar.txt # Copy and rename file quickly if not changedDeleting Files
rm saman.txt # Delete file
rm -f|--force saman.txt # Delete file, ignore nonexistent files and never promptReading Files
cat saman.txt # Print all contents
less saman.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /saman to search for 'saman')
head saman.txt # Print top 10 lines of file
tail saman.txt # Print bottom 10 lines of file
tail -f|--follow saman.txt # Print bottom 10 lines of file updating with new data
open saman.txt # Open file in the default editor
wc saman.txt # List number of lines words and characters in the fileSorting Files
sort saman.txt # Sort file (ascending order)
sort -r|--reverse saman.txt # Sort file (descending order)
sort -n|--numeric-sort saman.txt # Sort numbers instead of strings
sort -t|--field-separator: -k 3n /saman/saman.txt # Sort by the third column of a file
File Permissions
#
Permission
rwx
Binary
7
read, write and execute
rwx
111
6
read and write
rw-
110
5
read and execute
r-x
101
4
read only
r--
100
3
write and execute
-wx
011
2
write only
-w-
010
1
execute only
--x
001
0
none
---
000
For a directory, execute means you can enter a directory.
User
Group
Others
Description
6
4
4
User can read and write, everyone else can read (Default file permissions)
7
5
5
User can read, write and execute, everyone else can read and execute (Default directory permissions)
u - User
g - Group
o - Others
a - All of the above
ls -l /saman.sh # List file permissions
chmod +100 saman.sh # Add 1 to the user permission
chmod -100 saman.sh # Subtract 1 from the user permission
chmod u+x saman.sh # Give the user execute permission
chmod g+x saman.sh # Give the group execute permission
chmod u-x,g-x saman.sh # Take away the user and group execute permission
chmod u+x,g+x,o+x saman.sh # Give everybody execute permission
chmod a+x saman.sh # Give everybody execute permission
chmod +x saman.sh # Give everybody execute permissionFinding Files
Find binary files for a command.
type -a wget # Display all locations of executable
which -a wget # Display all locations of executables
whereis wget # Find the binary, source, and manual page fileslocate uses an index and is fast.
updatedb # Update the index
locate saman.txt # Find a file
locate --ignore-case # Find a file and ignore case
locate f*.txt # Find a text file starting with 'f'find doesn't use an index and is slow.
find /path -name saman.txt # Find a file
find /path -iname saman.txt # Find a file with case insensitive search
find /path -name "*.txt" # Find all text files
find /path -name saman.txt -delete # Find a file and delete it
find /path -name "*.png" -exec pngquant {} # Find all .png files and execute pngquant on it
find /path -type f -name saman.txt # Find a file
find /path -type d -name saman # Find a directory
find /path -type l -name saman.txt # Find a symbolic link
find /path -type f -mtime +30 # Find files that haven't been modified in 30 days
find /path -type f -mtime +30 -delete # Delete files that haven't been modified in 30 daysFind in Files
grep 'saman' /bar.txt # Search for 'saman' in file 'bar.txt'
grep 'saman' /bar -r|--recursive # Search for 'saman' in directory 'bar'
grep 'saman' /bar -R|--dereference-recursive # Search for 'saman' in directory 'bar' and follow symbolic links
grep 'saman' /bar -l|--files-with-matches # Show only files that match
grep 'saman' /bar -L|--files-without-match # Show only files that don't match
grep 'saman' /bar -i|--ignore-case # Case insensitive search
grep 'saman' /bar -x|--line-regexp # Match the entire line
grep 'saman' /bar -C|--context 1 # Add N line of context above and below each search result
grep 'saman' /bar -v|--invert-match # Show only lines that don't match
grep 'saman' /bar -c|--count # Count the number lines that match
grep 'saman' /bar -n|--line-number # Add line numbers
grep 'saman' /bar --colour # Add colour to output
grep 'saman\|bar' /baz -R # Search for 'saman' or 'bar' in directory 'baz'
grep --extended-regexp|-E 'saman|bar' /baz -R # Use regular expressions
grep -E 'saman|bar' /baz -R # Use regular expressionsReplace in Files
sed 's/fox/bear/g' saman.txt # Replace fox with bear in saman.txt and output to console
sed 's/fox/bear/gi' saman.txt # Replace fox (case insensitive) with bear in saman.txt and output to console
sed 's/red fox/blue bear/g' saman.txt # Replace red with blue and fox with bear in saman.txt and output to console
sed 's/fox/bear/g' saman.txt > bar.txt # Replace fox with bear in saman.txt and save in bar.txt
sed -i|--in-place 's/fox/bear/g' saman.txt # Replace fox with bear and overwrite saman.txt
sed -i|--in-place '/red fox/i\blue bear' saman.txt # Insert blue bear before red fox and overwrite saman.txt
sed -i|--in-place '/red fox/a\blue bear' saman.txt # Insert blue bear after red fox and overwrite saman.txt
sed -i|--in-place '10s/find/replace/' saman.txt # Replace the 10th line of the file
sed -i|--in-place '10,20s/find/replace/' saman.txt # Replace in the file 10-20 lines File Editor
nano # Open a new file in nano
nano saman.txt # Open a specific file
nano -m|--mouse saman.txt # Enable the use of the mouse
nano -l|--linenumbers saman.txt # Show line numbers in front of the text
nano +line,10 saman.txt # Open file positioning the cursor at the specified line and column
nano -B|--backup saman.txt # Create a backup file (`saman~`) when saving editsSymbolic Links
ln -s|--symbolic saman bar # Create a link 'bar' to the 'saman' folder
ln -s|--symbolic -f|--force saman bar # Overwrite an existing symbolic link 'bar'
ls -l # Show where symbolic links are pointingCompressing Files
zip
Compresses one or more files into *.zip files.
zip saman.zip /bar.txt # Compress bar.txt into saman.zip
zip saman.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into saman.zip
zip saman.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into saman.zip
zip -r|--recurse-paths saman.zip /bar # Compress directory bar into saman.zipgzip
Compresses a single file into *.gz files.
gzip /bar.txt saman.gz # Compress bar.txt into saman.gz and then delete bar.txt
gzip -k|--keep /bar.txt saman.gz # Compress bar.txt into saman.gztar -c
Compresses (optionally) and combines one or more files into a single *.tar, *.tar.gz, *.tpz or *.tgz file.
tar -c|--create -z|--gzip -f|--file=saman.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into saman.tgz
tar -c|--create -z|--gzip -f|--file=saman.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into saman.tgz
tar -c|--create -z|--gzip -f|--file=saman.tgz /bar # Compress directory bar into saman.tgzDecompressing Files
unzip
unzip saman.zip # Unzip saman.zip into current directorygunzip
gunzip saman.gz # Unzip saman.gz into current directory and delete saman.gz
gunzip -k|--keep saman.gz # Unzip saman.gz into current directorytar -x
tar -x|--extract -z|--gzip -f|--file=saman.tar.gz # Un-compress saman.tar.gz into current directory
tar -x|--extract -f|--file=saman.tar # Un-combine saman.tar into current directoryPackages
apt update # Refreshes repository index
apt search wget # Search for a package
apt show wget # List information about the wget package
apt list --all-versions wget # List all versions of the package
apt install wget # Install the latest version of the wget package
apt install wget=1.2.3 # Install a specific version of the wget package
apt remove wget # Removes the wget package
apt upgrade # Upgrades all upgradable packages
apt clean # Clears out the local repository of downloaded package files
dpkg -i|--install package_name.deb # Install deb file
rpm -i|--install package_name.rpm # Install rpm file Install package source code
tar zxvf sourcecode.tar.gz
cd sourcecode
./configure
make
make installDisk Usage
df # List disks, size, used and available space
df -h|--human-readable # List disks, size, used and available space in a human readable format
du # List current directory, subdirectories and file sizes
du /saman/bar # List specified directory, subdirectories and file sizes
du -h|--human-readable # List current directory, subdirectories and file sizes in a human readable format
du -d|--max-depth # List current directory, subdirectories and file sizes within the max depth
du -d 0 # List current directory sizeMemory Usage
free # Show memory usage
free -h|--human # Show human readable memory usage
free -h|--human --si # Show human readable memory usage in power of 1000 instead of 1024
free -s|--seconds 5 # Show memory usage and update continuously every five secondsShutdown and Reboot
shutdown # Shutdown in 1 minute
shutdown now # Immediately shut down
shutdown +5 # Shutdown in 5 minutes
shutdown -r|--reboot # Reboot in 1 minute
shutdown -r|--reboot now # Immediately reboot
shutdown -r|--reboot +5 # Reboot in 5 minutes
shutdown -c # Cancel a shutdown or reboot
reboot # Reboot now
reboot -f # Force a rebootIdentifying Processes
top # List all processes interactively
htop # List all processes interactively
ps ax # List all processes
pidof saman # Return the PID of all saman processes
CTRL+Z # Suspend a process running in the foreground
bg # Resume a suspended process and run in the background
fg # Bring the last background process to the foreground
fg 1 # Bring the background process with the PID to the foreground
sleep 30 & # Sleep for 30 seconds and move the process into the background
jobs # List all background jobs
jobs -p # List all background jobs with their PID
lsof # List all open files and the process using them
lsof -itcp:4000 # Return the process listening on port 4000Process Priority
Process priorities go from -20 (highest) to 19 (lowest).
nice -n -20 saman # Change process priority by name
renice 20 PID # Change process priority by PID
ps -o ni PID # Return the process priority of PIDKilling Processes
CTRL+C # Kill a process running in the foreground
kill PID # Shut down process by PID gracefully. Sends TERM signal.
kill -9 PID # Force shut down of process by PID. Sends SIGKILL signal.
pkill saman # Shut down process by name gracefully. Sends TERM signal.
pkill -9 saman # force shut down process by name. Sends SIGKILL signal.
killall saman # Kill all process with the specified name gracefully.Date & Time
date # Print the date and time
date --iso-8601 # Print the ISO8601 date
date --iso-8601=ns # Print the ISO8601 date and time
date -s "02 DEC 2020 12:02:02" # Manually change date and time
dpkg-reconfigure tzdata # Change date/timezone
uptime # Print how long the system has been running
time tree # Print amount of time to tree takes to executeScheduled Tasks
* * * * *
Minute, Hour, Day of month, Month, Day of the weekcrontab -l # List cron tab
crontab -e # Edit cron tab in a file editor
crontab /path/crontab # Load cron tab from a file
crontab -l > /path/crontab # Save cron tab to a file
* * * * * saman # Run saman every minute
*/15 * * * * saman # Run saman every 15 minutes
0 * * * * saman # Run saman every hour
15 6 * * * saman # Run saman daily at 6:15 AM
44 4 * * 5 saman # Run saman every Friday at 4:44 AM
0 0 1 * * saman # Run saman at midnight on the first of the month
0 0 1 1 * saman # Run saman at midnight on the first of the year
at -l # List scheduled tasks
at -c 1 # Show task with ID 1
at -r 1 # Remove task with ID 1
at now + 2 minutes # Create a task in a file editor to execute in 2 minutes
at 12:34 PM next month # Create a task in a file editor to execute at 12:34 PM next month
at tomorrow # Create a task in a file editor to execute tomorrowUser Management
sudo su # Switch to root user
sudo saman # Execute commands(has permission denied) as the root user
sudo nano /saman/saman.txt # Open directories and files(is not writable) as the root user
su username # Switch to a different user
passwd # To change the password of a user
adduser username # To add a new user
userdel username # To remove user
userdel -r|--remove username # To remove user with home directory and mail spool
usermod -a|--append -G|--groups GROUPNAME USERNAME # To add a user to a group
deluser USER GROUPNAME # To remove a user from a group
last # Display information of all the users logged in
last username # Display information of a particular user
w # Display who is onlineHTTP Requests
curl https://example.com # Return response body
curl -i|--include https://example.com # Include status code and HTTP headers
curl -L|--location https://example.com # Follow redirects
curl -O|--remote-name saman.txt https://example.com # Output to a text file
curl -H|--header "User-Agent: saman" https://example.com # Add a HTTP header
curl -X|--request POST -H "Content-Type: application/json" -d|--data '{"saman":"bar"}' https://example.com # POST JSON
curl -X POST -H --data-urlencode saman="bar" http://example.com # POST URL Form Encoded
wget https://example.com/file.txt # Download a file to the current directory
wget -O|--output-document saman.txt https://example.com/file.txt # Output to a file with the specified nameNetwork Troubleshooting
ifconfig # Display all network card and interface information
ifconfig -a # Display information of all network cards (including those that are not started at boot)
ifconfig eth0 # Display specific device information
ifconfig eth0 up # Turn on the network card
ifconfig eth0 down # Turn off the network card
ifconfig eth0 192.168.120.56 # Configure IP address for network card
curl ifconfig.me # Obtain external IP address
ping example.com # Send multiple ping requests using the ICMP protocol
ping -c 10 -i 5 example.com # Make 10 attempts, 5 seconds apart
ip addr # List IP addresses on the system
ip route show # Show IP addresses to router
netstat -i|--interfaces # List all network interfaces and in/out usage
netstat -l|--listening # List all open ports
traceroute example.com # List all servers the network traffic goes through
mtr -w|--report-wide example.com # Continually list all servers the network traffic goes through
mtr -r|--report -w|--report-wide -c|--report-cycles 100 example.com # Output a report that lists network traffic 100 times
nmap 0.0.0.0 # Scan for the 1000 most common open ports on localhost
nmap 0.0.0.0 -p1-65535 # Scan for open ports on localhost between 1 and 65535
nmap 192.168.4.3 # Scan for the 1000 most common open ports on a remote IP address
nmap -sP 192.168.1.1/24 # Discover all machines on the network by ping'ing themDNS
dig example.com # Show query information of domain A records
dig -4 example.com # Show IPv4 A records
dig -6 example.com # Show IPv6 AAA records
dig example.com @nameserver # Show query of a specific nameserver
dig example.com -p 123 # Show query of a specific port number
cat /etc/resolv.conf # Nameservers file
cat /etc/systemd/resolved.conf # DNS resolver config fileHardware
lsusb # List USB devices
lspci # List PCI hardware
lshw # List all hardwareSystem Information
uname -s # Print kernel name
uname -r # Print kernel release
uname -m # Print Architecture
uname -o # Print Operating System
uname -a # Print all Systen info
lsb_release -a # Print distribution-specific information
dpkg --print-architecture # Print-architecture by name
cat /proc/cpuinfo # Show cpu info
cat /proc/meminfo # Show memory info
Terminal Multiplexers
Start multiple terminal sessions. Active sessions persist reboots. tmux is more modern than screen.
tmux # Start a new session (CTRL-b + d to detach)
tmux ls # List all sessions
tmux attach -t 0 # Reattach to a session
screen # Start a new session (CTRL-a + d to detach)
screen -S saman # Start a new named session
screen -ls # List all sessions
screen -R 31166 # Reattach to a session
exit # Exit a session
reset # Reset the terminal(when binary and the terminal state is messed up)Secure Shell Protocol (SSH)
ssh hostname # Connect to hostname using your current user name over the default SSH port 22
ssh -i saman.pem hostname # Connect to hostname using the identity file
ssh user@hostname # Connect to hostname using the user over the default SSH port 22
ssh user@hostname -p 8765 # Connect to hostname using the user over a custom port
ssh ssh://user@hostname:8765 # Connect to hostname using the user over a custom portSet default user and port in ~/.ssh/config, so you can just enter the name next time:
$ cat ~/.ssh/config
Host name
User saman
Hostname 127.0.0.1
Port 8765
$ ssh nameSecure Copy
scp saman.txt ubuntu@hostname:/home/ubuntu # Copy saman.txt into the specified remote directory
scp ubuntu@hostname:/home/ubuntu/saman.txt /C:\Users\Admin # Copy saman.txt from the specified remote directoryBash Profile
bash -
.bashrczsh -
.zshrc
# Always run ls after cd
function cd {
builtin cd "$@" && ls
}
# Prompt user before overwriting any files
alias cp='cp --interactive'
alias mv='mv --interactive'
alias rm='rm --interactive'
# Always show disk usage in a human readable format
alias df='df -h'
alias du='du -h'Conditional Statements
Boolean Operators
$saman- Is true!$saman- Is false
Numeric Operators
-eq- Equals-ne- Not equals-gt- Greater than-ge- Greater than or equal to-lt- Less than-le- Less than or equal to-esaman.txt - Check file exists-zsaman - Check if variable exists
String Operators
=- Equals==- Equals-z- Is null-n- Is not null<- Is less than in ASCII alphabetical order>- Is greater than in ASCII alphabetical order
If Statements
#!/bin/bash
[[
if [[$saman = 'bar']]; then
echo 'one'
elif [[$saman = 'bar']] || [[$saman = 'baz']]; then
echo 'two'
elif [[$saman = 'ban']] && [[$USER = 'bat']]; then
echo 'three'
else
echo 'four'
fi
]]Inline If Statements
#!/bin/bash
[[ $USER = 'saman' ]] && echo 'yes' || echo 'no'While Loops
#!/bin/bash
[
declare -i counter
counter=10
while [$counter -gt 2]; do
echo The counter is $counter
counter=counter-1
done
]For Loops
#!/bin/bash
for i in {0..10..2}
do
echo "Index: $i"
done
for filename in file1 file2 file3
do
echo "Content: " >> $filename
done
for filename in *;
do
echo "Content: " >> $filename
doneCase Statements
#!/bin/bash
echo "What's the weather like tomorrow?"
read weather
Last updated