# Bash cheat sheet

## Navigate the Filesystem

* `pwd` ~ view current directory
    
* `cd` ~ move into a directory
    
    * `..` ~ move up a directory
        
* `ls` ~ list what is in a directory
    
    * `-a` ~ hidden files and folders
        
    * `-l` ~ long listing, see more information
        

## View Files and Folders

* `cat` ~ see content of a file
    
    * `-n` ~ see content with line numbers
        
* `less` ~ see content of a file in editor
    
* `open` ~ open files in the directory
    

## Create and Delete Files and Folders

* `touch` ~ create files
    
* `mkdir` ~ create folders
    
    * `-p` ~ create nested folders `a/b/c`
        
* `echo` ~ log string or write to file
    
    * `>` ~ write to file
        
    * `>>` ~ append at the end of file
        
* `rm` ~ remove file or folder
    
    * `-r` ~ remove folder recursively
        

## Move and Copy Files and Folders

* `mv` ~ used to move and rename files and folders
    
    * `mv source/* target/` ~ move everything inside source to target folder
        
* `cp` ~ copy files and folders
    
    * `cp -R source/* target/` ~ copy everything recursively from source to target folder
        

## Find Files and Folders

* `find` ~ find files and folders
    
    * `find images/ -name "*.png"` ~ find files that end with `png` .
        
        * `-iname` ~ find files, but case insensitive
            
    * `find . -type d -name "images"` ~ find all folders in current directory with name **images**
        
    * `-delete` ~ flag to delete what was found
        

## Search for Text

* `grep` ~ search for text
    
    * `grep "text" folder/file.js` ~ search for text in whatever file
        
    * `--color` ~ search but colorize what we're looking for
        
    * `-n` ~ include the line numbers
        
    * `-e` ~ search but use regex
        
    * `man grep` ~ see all flags available
        

## Make HTTP Requests

* `curl` ~ make requests, by default GET
    
    * `-i` ~ inspect headers
        
    * `-iL` ~ inspect headers and follow redirect to see response
        
    * `curl -iL "..."`
        
    * `-H` ~ pass headers
        
    * `curl -H "Authorization: ..."`
        
    * `-X` ~ change the request method
        
    * `curl -X POST -H "Content-Type: ..." -d '{ title: "Curling" }'`
        
    * `\` ~ to do things on new lines nicely formatted
        
    * `curl -i -X PUT \`
        

## Create and Run Scripts

* `.sh` ~ file has to end with this
    
* `chmod x+u ./file.sh` ~ make file executable
    
    * The command stands for change mode, giving the user the executable permissions
        
* `$` ~ Accept arguments in your script. They will be passed in chronological order when running the script: `./file.sh argument1 argument2`
    
* `$(<command>)` ~ run commands inside the bash script
    
* `#` ~ write comments in bash
    

## Store and Use Values

* `var=value` ~ set a variable's value for a session
    
* `echo $var` ~ print the variable
    
* `unset var` ~ unset the variable
    
* `export var` ~ make the variable available to all child processes
    

## Understand and Use Functions

Create and call a function in bash:

```bash
hi() {
    echo "Hello world"
}

hi
```

Function with an argument passed:

```bash
hi() {
    echo "$1 world"
}

hi "Hello"
```

Assign function's return statement to a variable:

```bash
hi() {
    echo "$1 world"
}

hiResult=$(hi "Hello")

echo "the result from hi is $hiResult"
```

* `local` ~ create local variables only available within the function
    

## Understand Exit Statuses

* `echo $?` ~ see the exit status
    
* `0` for ok
    
* `1` for error
    

## Use Conditional Statements

```bash
# Some conditional primaries that can be used in the if expression:
#   =, !=      string (in)equality
#   -eq, -ne   numeric (in)equality
#   -lt, -gt   less/greater than
#   -z         check variable is not set
#   -e         check file/folder exists
#    elif      else if statement

if [[ $USER = 'naruto' ]]; then
  echo "true"
else
  echo "false"
fi
```

```bash
# Inline format, similar to ternaries

[[ $USER = 'naruto' ]] && echo "yes" || echo "no"
```

## Create Aliases in .bash\_profile

* On Ubuntu, if you don't create the `.bash_profile` file, it will use the existing configuration file `~/.profile` .
    
* `gitm="git add . && git commit -m 'commit'"` ~ example of an alias
    

## Create and Copy multiple files with Brace Expansions

* Items in the list of brackets.
    
* `touch index.js{,.backup}` ~ create two files, `index.js` and `index.js.backup` , first item in the list is empty
    
* `mkdir -p packages/{pkg1,pkg2,pkg3}/src` ~ create multiple packages inside `packages` folder, each containing `src` folder
    
* `echo {1..10}` , `echo {a..z}` ~ print out ranges
    
* You can use it for other things like creating multiple files
    

## History expansion

* `!!` ~ run the previous command
    

## Default arguments

* `dir=${1:-$PWD}` ~ users would pass the directory as the first argument, but it defaults to the current directory
    

## Bash Keyboard Shortcuts

* **Ctrl+A** - go to the beginning of a line
    
* **Ctrl+E**\- go to the end of a line
    
* **Ctrl+K** - clears line up to the cursor
    
* **Ctrl+W** - delete last word
    
* **Ctrl+L** - clear the screen (equivalent of the `clear` command)
    

## Complicated Conditional Statements

Case statements, they can also be on multiple lines:

```bash
case "$1" in
  firstValue) echo "firstValue matched";;
  secondValue) echo "secondValue matched";;
  thirdValue) 
    echo "thirdValue matched"
  ;;
esac
```