Bash Cheatsheet

bash-cheatsheet.sh

# Create a file and insert some text with the ">" operator
echo "my new site" > index.html

# Show PATH
echo $PATH # /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

# /usr/local/bin is in the PATH by default

# Create symbolic link (symlink)
ln -s "/Applications/Sublime Text.app/Contents/SharedSupport/bin/subl" /usr/local/bin/sublime
# > sublime <filename>

# Display text file in shell
cat config.json

# Display long text file in shell
less config.json

# Show hidden files
ls -a

# Download file and specifiy target file name
wget http://bit.ly/Hqv9aj -O jfrog-artifactory-oss-4.4.2.zip

# Execute programmB only if programmA exits with an exit code of 0
programmA && programmB

# Execute programmB only if programmA exits withn an exit code other than 0
programmA || programmB

# Use a pipe symbol to set the stdout of a programm to the stdin of another programm
programmA | programmB

# Set variable
name=value

# Use variable
$name

# OR:
${name}

# Display path of executable (e.g. npm)
which npm

# Clear console
clear

# List all installed apt packages
apt list --installed

# Place of sudo config
/etc/sudoers

# List files + Sort them + "less" them
ls <dir> | sort | less

# Print current working directory
pwd

# Create an alias for a command or a list of commands
alias home='cd ~'

# Show current bash version
bash --version

# Usable shells config
/etc/shells

# Change shell for current user
chsh -s /usr/local/Cellar/bash/4.4_1/bin/bash

# Show currently logged in users with login date
who

# Print to the console
echo Hey Ho Lets go
# OR
echo "Hey Ho Lets go"

# Append text to file via cat (=concatenate). End input with Ctrl+D
cat >> file.txt
Type in
random Text

# Show line/word/character count for a file
wc myfile.txt

# Show only line/word/character count for a file
wc [-l] [-w] [-c] myfile.txt

# List files with specific file extension
ls *.txt

# Remove multiple files
rm fileOne.txt fileTwo.txt

# Create multiple files
touch fileOne.txt fileTwo.txt

# Go to previous working directory
cd -

# Remove directory with files recursively (rmdir <dirname> can only remove empty directories)
rm -r <dirname>

# Show more info with ls -l (=long)
ls -l

# Example output ls -l
-rw-r--r--  1 ekip  staff  2133 30 Okt 19:56 bash-cheatsheet.sh

# Format
Type+Rights Links Owner Group Size Modified Name

# Value descriptions from left to right
# (x---------) Filetype
- normal file
d directory
p named pipe
c character oriented device file
b block oriented device file
s unix domainsocket
l symlink

# POSIX Rights
# (-rwx------) Owner rights
# (----rwx---) Group rights 
# (-------rwx) All other users rights 

r read right
w write right
x execute right

# Symlink count
1 if there is no reference to this file

# Owners username
ekip

# Groups name which is defined by the owner
staff

# Filesize in bytes
2133

# Last modified date + time
30 Okt 19:56

# Filename
bash-cheatsheet.sh

# Show current Date
date

# Show current user
whoami

# Show all logged in users
who

# Show hostname
hostname

# Make a file executable for the owner
chmod u+x myexecutablefile

# Show processes of current shell
ps -f

# Execute process without STDOUT on screen
./my-script 1>/dev/null

# Run process in background
./my-script &

# Kill process (send SIGTERM -> can be ignored by the process)
kill 123

# Force kill process (send SIGKILL -> cannot be ignored by the process)
kill -9 123

# Kill last started background process
kill $!

# Execute script with Bourne-Shell
sh my-script

# Execute script with Korn-Shell
ksh my-script

# Set executing Shell within the first line of the script (Shebang)
#!<absolute-path-of-shell>

# Set Korn-Shell as executing Shell
#!/bin/ksh

# OR
#!/usr/bin/ksh

# Set Bash-Shell as executing Shell
#!/bin/bash

# OR
#!/usr/bin/bash

# Set Bourne-Shell as executing Shell
#!/bin/sh

# OR
#!/usr/bin/sh

# Execute script without Sub-Shell
# 
# As shellscripts are started in a Sub-Shell (not in the current Shell)
# there is no way to change the environment variables of the current Shell.
# To execute a script within the current Shell just add a ". " before the script name.
. ./my-script

# OR with Bash-Shell there is the "source" command as an alternative to the dot notation
source ./my-script

# Show current Shell within script
$SHELL

# Split long command to two lines with a "\" after the first line
echo "This is a long text\
  separated with backslashes\
  within the script"

# Exit current script with exit code number 0-255
# Where 0 stands for "Everything worked fine"
# And all other numbers for "Something went wrong"
exit <exit-code>

# Exit with the exit code of the last executed command in the script
exit

# Show exit code of last executed script
echo $?

# Debug a script with -x option to output executed line with a prefixed "+"
# just before the execution
bash -x ./my-script

# Replace the "+" with a more meaningful name by setting the PS4 environment variable
export PS4='[--- Line: $LINENO ---] '

# Show current process id
echo $$

# Show home directory of current user
echo $HOME

# Program which works like a task manager on the console
top

# Check if the current shell is a login shell (a "-" before the shell name)
> ps -f
... -bash

# Find lines in file(s) by a specific search value
grep <search-value> <filename> [<filename>, ...]

# Find lines recursively by a specific search value
grep -r <search-value> <directory>

# Find files/directories by name (case-sensitive)
find <search-root-directory> -name <search-value>

# Find files/directories by name (case-insensitive)
find <search-root-directory> -iname <search-value>

# Find directories by name
find <search-root-directory> -type d -name <search-value>

# Find files by name
find <search-root-directory> -type f -name <search-value>

# Find all files with .test.js in its filename
find . -name "*.test.js"

# Find lines within files found by the find command
find <directory> -name <filename> | xargs grep <search-value>

# Find lines within .test.js files with "describe(" in it
find . -name "*.test.js" | xargs grep "describe("

# Only find lines within files tracked by Git
git grep <search-value>

# Highlight search values red within the result list of grep
grep --color <search-value> .

# Substitute call within bash command (called command substitution)
cat $(which idea)

# Lookup process using a specific port
lsof -i :1337

# OR
lsof -nP -i4TCP:1337 | grep LISTEN

# Watch or "run the same command over and over again"
watch <command>

# e.g. Watch conteiners within you local machine
watch docker container ls