Linux / Bash Cheat Sheet#
A cheat sheet for the Linux command line, primarily for the bash shell.
Command History#
!! # Run the last command
touch foo.sh
chmod +x !$ # !$ is the last argument of the last command i.e. foo.sh
history # Lists the last 15 commands executes. history -n lists the last n commands
!n # Run the numbered command from history
Creating Directories#
mkdir foo # Create a directory
mkdir foo bar # Create multiple directories
mkdir -p|--parents foo/bar # Create nested directory
mkdir -p|--parents {foo,bar}/baz # Create multiple nested directories
mktemp -d|--directory # Create a temporary directory
Moving Directories#
cp -R|--recursive foo bar # Copy directory
mv foo bar # Move directory
rsync -z|--compress -v|--verbose /foo /bar # Copy directory, overwrites destination
rsync -a|--archive -z|--compress -v|--verbose /foo /bar # Copy directory, without overwriting destination
rsync -avz /foo username@hostname:/bar # Copy local directory to remote directory
rsync -avz username@hostname:/foo /bar # Copy remote directory to local directory
Deleting Directories#
rmdir foo # Delete empty directory
rm -r|--recursive foo # Delete directory including contents
rm -r|--recursive -f|--force foo # Delete directory including contents, ignore nonexistent files and never prompt
Creating Files#
touch foo.txt # Create file or update existing files modified timestamp
touch foo.txt bar.txt # Create multiple files
touch {foo,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 file
Standard Output, Standard Error and Standard Input#
echo "foo" > bar.txt # Overwrite file with content
echo "foo" >> 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 2>&1 > out.txt # Redirect standard output and error to a file
ls > /dev/null # Discard standard output and error
read foo # Read from standard input and write to the variable foo
Moving Files#
cp foo.txt bar.txt # Copy file
mv foo.txt bar.txt # Move file
rsync -z|--compress -v|--verbose /foo.txt /bar # Copy file quickly if not changed
rsync z|--compress -v|--verbose /foo.txt /bar.txt # Copy and rename file quickly if not changed
Deleting Files#
rm foo.txt # Delete file
rm -f|--force foo.txt # Delete file, ignore nonexistent files and never prompt
tldr pages: rm
Reading Files#
cat foo.txt # Print all contents
less foo.txt # Print some contents at a time (g - go to top of file, SHIFT+g, go to bottom of file, /foo to search for 'foo')
head foo.txt # Print top 10 lines of file
tail foo.txt # Print bottom 10 lines of file
open foo.txt # Open file in the default editor
wc foo.txt # List number of lines words and characters in the 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 /foo.sh # List file permissions
chmod +100 foo.sh # Add 1 to the user permission
chmod -100 foo.sh # Subtract 1 from the user permission
chmod u+x foo.sh # Give the user execute permission
chmod g+x foo.sh # Give the group execute permission
chmod u-x,g-x foo.sh # Take away the user and group execute permission
chmod u+x,g+x,o+x foo.sh # Give everybody execute permission
chmod a+x foo.sh # Give everybody execute permission
chmod +x foo.sh # Give everybody execute permission
Finding Files#
Find binary files for a command.
type wget # Find the binary
which wget # Find the binary
whereis wget # Find the binary, source, and manual page files
tldr pages: type which whereis
locate uses an index and is fast.
updatedb # Update the index
locate foo.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 foo.txt # Find a file
find /path -iname foo.txt # Find a file with case insensitive search
find /path -name "*.txt" # Find all text files
find /path -name foo.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 foo.txt # Find a file
find /path -type d -name foo # Find a directory
find /path -type l -name foo.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 days
tldr pages: find
Find in Files#
grep 'foo' /bar.txt # Search for 'foo' in file 'bar.txt'
grep 'foo' /bar -r|--recursive # Search for 'foo' in directory 'bar'
grep 'foo' /bar -R|--dereference-recursive # Search for 'foo' in directory 'bar' and follow symbolic links
grep 'foo' /bar -l|--files-with-matches # Show only files that match
grep 'foo' /bar -L|--files-without-match # Show only files that don't match
grep 'Foo' /bar -i|--ignore-case # Case insensitive search
grep 'foo' /bar -x|--line-regexp # Match the entire line
grep 'foo' /bar -C|--context 1 # Add N line of context above and below each search result
grep 'foo' /bar -v|--invert-match # Show only lines that don't match
grep 'foo' /bar -c|--count # Count the number lines that match
grep 'foo' /bar -n|--line-number # Add line numbers
grep 'foo' /bar --colour # Add colour to output
grep 'foo\|bar' /baz -R # Search for 'foo' or 'bar' in directory 'baz'
grep --extended-regexp|-E 'foo|bar' /baz -R # Use regular expressions
egrep 'foo|bar' /baz -R # Use regular expressions
Replace in Files#
sed 's/fox/bear/g' foo.txt # Replace fox with bear in foo.txt and output to console
sed 's/fox/bear/gi' foo.txt # Replace fox (case insensitive) with bear in foo.txt and output to console
sed 's/red fox/blue bear/g' foo.txt # Replace red with blue and fox with bear in foo.txt and output to console
sed 's/fox/bear/g' foo.txt > bar.txt # Replace fox with bear in foo.txt and save in bar.txt
sed 's/fox/bear/g' foo.txt -i|--in-place # Replace fox with bear and overwrite foo.txt
tldr pages: sed
Symbolic Links#
ln -s|--symbolic foo bar # Create a link 'bar' to the 'foo' folder
ln -s|--symbolic -f|--force foo bar # Overwrite an existing symbolic link 'bar'
ls -l # Show where symbolic links are pointing
tldr pages: ln
Compressing Files#
zip#
Compresses one or more files into *.zip files.
zip foo.zip /bar.txt # Compress bar.txt into foo.zip
zip foo.zip /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.zip
zip foo.zip /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.zip
zip -r|--recurse-paths foo.zip /bar # Compress directory bar into foo.zip
tldr pages: zip
gzip#
Compresses a single file into *.gz files.
gzip /bar.txt foo.gz # Compress bar.txt into foo.gz and then delete bar.txt
gzip -k|--keep /bar.txt foo.gz # Compress bar.txt into foo.gz
tldr pages: gzip
tar -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=foo.tgz /bar.txt /baz.txt # Compress bar.txt and baz.txt into foo.tgz
tar -c|--create -z|--gzip -f|--file=foo.tgz /{bar,baz}.txt # Compress bar.txt and baz.txt into foo.tgz
tar -c|--create -z|--gzip -f|--file=foo.tgz /bar # Compress directory bar into foo.tgz
tldr pages: tar
Decompressing Files#
unzip#
unzip foo.zip # Unzip foo.zip into current directory
tldr pages: unzip
gunzip#
gunzip foo.gz # Unzip foo.gz into current directory and delete foo.gz
gunzip -k|--keep foo.gz # Unzip foo.gz into current directory
tldr pages: gunzip
tar -x#
tar -x|--extract -z|--gzip -f|--file=foo.tar.gz # Un-compress foo.tar.gz into current directory
tar -x|--extract -f|--file=foo.tar # Un-combine foo.tar into current directory
tldr pages: tar
Disk 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 /foo/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 size
Memory 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 seconds
tldr pages: free
Packages#
Note: apt is for Ubuntu-based systems. For MacOS, look at Homebrew
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
tldr pages: apt
Shutdown and Reboot#
shutdown # Shutdown in 1 minute
shutdown now "Cya later" # Immediately shut down
shutdown +5 "Cya later" # Shutdown in 5 minutes
shutdown --reboot # Reboot in 1 minute
shutdown -r now "Cya later" # Immediately reboot
shutdown -r +5 "Cya later" # Reboot in 5 minutes
shutdown -c # Cancel a shutdown or reboot
reboot # Reboot now
reboot -f # Force a reboot
Identifying Processes#
top # List all processes interactively
htop # List all processes interactively
ps all # List all processes
pidof foo # Return the PID of all foo 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 4000
Process Priority#
Process priorities go from -20 (highest) to 19 (lowest).
nice -n -20 foo # Change process priority by name
renice 20 PID # Change process priority by PID
ps -o ni PID # Return the process priority of PID
Killing 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 foo # Shut down process by name gracefully. Sends TERM signal.
pkill -9 foo # force shut down process by name. Sends SIGKILL signal.
killall foo # 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
time tree # Time how long the tree command takes to execute
Scheduled Tasks#
* * * * *
Minute, Hour, Day of month, Month, Day of the week
crontab -l # List cron tab
crontab -e # Edit cron tab in Vim
crontab /path/crontab # Load cron tab from a file
crontab -l > /path/crontab # Save cron tab to a file
* * * * * foo # Run foo every minute
*/15 * * * * foo # Run foo every 15 minutes
0 * * * * foo # Run foo every hour
15 6 * * * foo # Run foo daily at 6:15 AM
44 4 * * 5 foo # Run foo every Friday at 4:44 AM
0 0 1 * * foo # Run foo at midnight on the first of the month
0 0 1 1 * foo # Run foo 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 Vim to execute in 2 minutes
at 12:34 PM next month # Create a task in Vim to execute at 12:34 PM next month
at tomorrow # Create a task in Vim to execute tomorrow
HTTP 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 foo.txt https://example.com # Output to a text file
curl -H|--header "User-Agent: Foo" https://example.com # Add a HTTP header
curl -X|--request POST -H "Content-Type: application/json" -d|--data '{"foo":"bar"}' https://example.com # POST JSON
curl -X POST -H --data-urlencode foo="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 foo.txt https://example.com/file.txt # Output to a file with the specified name
Network Troubleshooting#
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 them
DNS#
host example.com # Show the IPv4 and IPv6 addresses
dig example.com # Show complete DNS information
cat /etc/resolv.conf # resolv.conf lists nameservers
Hardware#
lsusb # List USB devices
lspci # List PCI hardware
lshw # List all hardware
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 -ls # List all sessions
screen -R 31166 # Reattach to a session
exit # Exit a session
Secure Shell Protocol (SSH)#
ssh hostname # Connect to hostname using your current user name over the default SSH port 22
ssh -i foo.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 port
tldr page: ssh
Set default user and port in ~/.ssh/config, so you can just enter the name next time:
$ cat ~/.ssh/config
Host name
User foo
Hostname 127.0.0.1
Port 8765
$ ssh name
Using the SSH Config File
Secure Copy#
scp foo.txt ubuntu@hostname:/home/ubuntu # Copy foo.txt into the specified remote directory
tlrd page: scp
Bash Profile#
bash -
.bashrczsh -
.zshrc# Default shell for MacOS
# 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'
Bash Script#
Variables#
#!/bin/bash
foo=123 # Initialize variable foo with 123
declare -i foo=123 # Initialize an integer foo with 123
declare -r foo=123 # Initialize readonly variable foo with 123
echo $foo # Print variable foo
echo ${foo}_'bar' # Print variable foo followed by _bar
echo ${foo:-'default'} # Print variable foo if it exists otherwise print default
export foo # Make foo available to child processes
unset foo # Make foo unavailable to child processes
Environment Variables#
#!/bin/bash
env # List all environment variables
echo $PATH # Print PATH environment variable
export FOO=Bar # Set an environment variable
Functions#
#!/bin/bash
greet() {
local world = "World"
echo "$1 $world"
return "$1 $world"
}
greet "Hello"
greeting=$(greet "Hello")
Exit Codes#
#!/bin/bash
exit 0 # Exit the script successfully
exit 1 # Exit the script unsuccessfully
echo $? # Print the last exit code
Conditional Statements#
Boolean Operators#
$foo- Is true!$foo- 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-efoo.txt - Check file exists-zfoo - 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 [[$foo = 'bar']]; then
echo 'one'
elif [[$foo = 'bar']] || [[$foo = 'baz']]; then
echo 'two'
elif [[$foo = 'ban']] && [[$USER = 'bat']]; then
echo 'three'
else
echo 'four'
fi
Inline If Statements#
#!/bin/bash
[[ $USER = 'rehan' ]] && echo 'yes' || echo 'no'
While Loops#
#!/bin/bash
declare -i counter
counter=10
while [$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
done
Case Statements#
#!/bin/bash
echo "What's the weather like tomorrow?"
read weather
case $weather in
sunny | warm ) echo "Nice weather: " $weather
;;
cloudy | cool ) echo "Not bad weather: " $weather
;;
rainy | cold ) echo "Terrible weather: " $weather
;;
* ) echo "Don't understand"
;;
esac
License#
This material was taken from RehanSaeed/Bash-Cheat-Sheet under a MIT License:
Copyright (c) 2019 Muhammad Rehan Saeed
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.