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  • Command line
    • History
      • Shell: any program that users employ to type commands (-Wikipedia)
        • Interfaces directly with the OS kernal
          • Kernal is typically the lowest level component of an OS
      • First shell: Thompson shell
        • Written at Bell Labs in 1971
        • Lots of features for subsequent shells came from this one
      • First modern shells: Bourne shell & C shell
        • Bourne shell
          • 1979 at Bell Labs
          • Every current macOS & Linux distro comes with a version of this shell called bash
            • Bourne Again Shell
        • C shell
          • Bill Joy as grad student at UC-Berkeley in late 70s
      • Unix Shell
        • Serves as a command language and scripting language
        • bash
          • Written by Brian Fox in 1989 for the GNU project as free replacement for Bourne shell
          • Can enter commands or read them from a file (scripting)
          • Takes some features from C shell
    • Subjects
      • home directory
        • Your default starting location
        • Represented by ~
        • When opening a new terminal window, this is the default location
      • bash profile
        • stores user-specific information
        • found in home folder
        • ~/.bash_profile
          • sometimes you'll see ~/.bashrc instead
      • entering a command
        • [command] -[argument(s)] input
        • ls -a
        • grep npm
        • ls -al | grep npm
      • print to terminal
        • echo
      • present working directory
        • pwd
      • list directory contents
        • ls
          • list
        • common arguments
          • a: show all files & folders (even hidden)
          • h: show sizes in readable format
          • l: show in long list format
          • t: sort by modification time
      • make directory
        • mkdir
          • mkdir [directory]
      • change directory
        • cd
          • cd [directory]
      • create a file
        • touch
          • touch [filename]
          • can use with absolute path
      • determine file type
        • file
          • file [filename]
      • remove a file
        • rm
          • remove
          • common arguments
            • r: remove a directory and all its contents (recursive)
            • f: never prompt (force)
      • rename a file
        • mv
          • move
          • mv [oldname] [newname]
      • move a file
        • mv
          • move
          • mv [oldlocation] [newlocation]
      • copy a file
        • cp
          • copy
          • cp [origfile] [newfile]
            • If new file exists, it will overwrite new file
          • common options:
            • i: interactive; will prompt before overwriting
            • -R: copy a directory and all sub directories / files (recursive)
      • search file contents
        • cat
          • concatenate files and output in terminal
          • common arguments
            • n: Show line numbers in result
        • head
          • head of file
          • head [arguments] [file(s)]
          • common arguments
            • n: Shows only n lines in the file (head -100)
        • tail
          • tail (end) of file
          • tail [arguments] [file(s)]
          • common arguments
            • n: Shows only n lines in the file (tail -100)
        • grep
          • global regular expression print
          • grep [arguments] [phrase] [filelocation]
          • common arguments
            • i: ignore case
            • n: show line number in result
            • o: only show the matching words or phrases
      • file permissions
        • drwxr-xr-x 6 Brenna staff 204 Jun 27 16:58 terminal-exercises
          • drwxr-xr-x
          • 0: file type
            • -: normal file
            • d: directory
          • 1-9: permissions
            • r: read
            • w: write
            • x: execute
            • 1-3: file owner permissions
            • 4-6: group's permissions
            • 789: everyone else
          • 6: number of hard links
          • Brenna: owner name
          • staff: owner group
          • 204: file size
          • Jun...: last modified date
          • terminal-exercises: file / directory name
        • chmod
          • change mode
          • numbers method
          • chmod ###
            • read (r): 4
            • write (w): 2
            • execute (x): 1
            • owner > group > everyone
      • man pages
        • man
        • manual pages
        • man [command]
      • command shortcuts
        • ~
          • cd ~/Downloads
          • mv ~/Downloads/bacon.txt ~/school/terminal-exercises/
        • cd
        • .
          • reference current directory in commands
        • ..
          • reference next directory up in commands
          • cd ../Downloads
      • aliases
        • it's possible to create custom shortcut commands via aliases in your bash_profile
        • alias [name]='terminal command'
        • alias cf='touch'
        • alias gohome='cd ~'
        • alias project='cd ~/school && nvm use 6.11'
      • root / sudo
        • super user do
        • The 'admin' of the console
        • Required as a command when administrative action is required
        • The terminal window will prompt for password
        • Root is a synonym for super user
      • variables
        • last argument of last command
          • $_
        • home dir
          • $HOME
        • path
          • $PATH
          • Search path
          • When an unknown command is typed into the terminal, this comprises the list of directories it will search through to find the executable for the command
      • run multiple commands
        • &&
          • This will execute a command only if the previous command was successful
          • mkdir my-folder && cd $_
          • alias newfolder='mkdir new-folder && cd new-folder'
          • alias newfolder='mkdir new-folder && cd $_'
        • ;
          • This will execute commands regardless of whether or not the previous command succeeds
          • mkdir new-folder ; cd $_ && touch file-in-my-folder.txt
      • stdin, stdout, stderr (standard streams)
        • stdin (0)
          • standard input
          • Data fed into the program
        • stdout (1)
          • standard output
          • Data printed by the program
            • defaults to the terminal
        • stderr (2)
          • standard error
          • Messages & errors
            • defaults to the terminal
        • redirecting output
          • to a file
            • >
            • Will write stdout to a filename specified
            • Creates a new file if file does not exist
            • If file exists, will overwrite content
              • Use >> to append
            • ls > files.txt
            • echo 'some text' > textfile1.txt
            • echo 'some new text' > textfile1.txt
            • echo 'line 1 \nline 2' > textfile2.txt
            • cat textfile1.txt textfile2.txt > all-files.txt
          • to redirect stderr, specify the stream number (2) and the carrot 2>
            • from a file
            • <
            • redirects stdout from a file to the program
            • grep nomnomnom < bacon.txt
      • piping
        • sends data from one program to another
        • left output feeds into right output
        • ls . | grep npm
      • top
        • table of processes
        • top
        • provides a real-time view of current running processes in the OS
        • similar to task manager in windows
      • kill
        • kill
        • terminates a currently running process
        • kill [process id]
      • compress / uncompress
        • tar
        • tape archive
        • also commonly called a 'tarball'
        • common options
          • c: create an archive
          • v: verbose; displays all files added to the tarball
          • f: specify the filename
          • x: extract the archive
          • C: changes to specified directory
          • t: list contents of archive
          • z: create a gzip archive
        • tar -cvf example.tar my-project/ (compress)
        • tar -xvf example.tar (uncompress)
          • uncompresses in current directory
        • there is also a zip command
      • autocomplete
        • tab
        • Terminal will try to autocomplete directories or files as you type them in
      • ide commands
        • atom
        • subl
        • vim
      • scripting
        • it's also possible to create a file that's a series of commands and execute it
        • this is very common in dev ops work, and a very useful skill
        • sh or bash
        • sh [filename]
        • Can append any number of commands