CSEC

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Shell commands ​

ls ​

(lists contents of directory)

some flags

-la or -latrh

you can also pass in file paths like

ls Documents/

You can also combine both

cd ​

Allows you to change directorys

e.g.

cd Documents

pwd ​

prints working directory

echo ​

Lets you print some text

touch ​

lets you create a file or update its modified date

cp ​

copy file or directory to target destination

cp <target> <destination>

sudo ​

Execute a command as another user

sudo [Command]
  • sudo allows a permitted user to execute a command as the superuser.
  • Commonly used when installing packages

su ​

Substitute user identity

sudo su
  • Typically used as above to it switches user identities temporarily to the superuser

passwd ​

changes a users password

  • used by itself it changes a current users password
  • used w/ a username it'l change that users password
passwd username

useradd ​

useradd is a command in Linux that is used to add user accounts to your system

useradd [options] [User_name]

mkdir ​

Create directories / folders

mkdir [name]

wget ​

Download files from the web

wget [URL]

tar ​

Archiving Utility, usually combined w/ a compression method like gzip or bzip2

  • E[x]tract a (compressed) archive [f]ile into the current directory [v]erbosely:
tar xfv [path/to/source.tar]

chown ​

Change user and group ownership of files and directories

chown [user] [path/to/file_or_dir]

mv ​

like copy, but it moves files to new destinations

mv <target> <destination>

rm ​

Deletes files

rm hello.txt

to delete directorys with items inside (this is a safe delete)

rm -r hello
rm -rf hello (force delete recursivly)

ln ​

Creates symlink to a file in a another location

with -s == symlink, w/out hard link

ln -s hello.txt symlink.txt
lrwxrwxrwx  1 baytizzel baytizzel    9 May  3 09:26 symlink.txt -> hello.txt

essentially doing this, both files will update with each other

less ​

View text content in a scrollable fassion

  • allows you to also search as well

more ​

Less than less, allows you to only go forware

man ​

The manual, good resource to learn tools

man <command>

tldr ​

Another great tool like man

too long didnt read

grep ​

Pattern matches against text content

grep 'string' <file>

find ​

finds file in directorys

since syntax might be weird a better command is

fd ​

easier to use find

fd <file>

sed ​

stream editor, used to find and replace text

(not sure on this one too much)

awk ​

tool to extract data from specific text.

  • I tend to use it for log analysis
  • Its actually a programming language??

sort ​

Sorts text contents (defaults to alphabetic)

sort (Alphabetic)
sort -n (numeric)
sort -R (random)

Lets you see first few lines of a file

head hello.txt

can pass in the number of lines w/ -n

tail ​

lets you see last few lines of a file

tail hello.txt

tail -f log (follows as new lines are appended to file)

Piping | ​

Take output from one command, and pass it into the next command.

e.g.

echo 'Hello, World!' | sed 's/word/universe/'
Hello, universe!

xargs ​

Takes content of what you pipe into it, and split it to different chunks

ls | grep 'l' | xargs du -sh
124M lean-mean-svelte-machine
140K log

I don't know how this works, and it doesn't work well on my machine sadge

Subshell ​

You can essentiall run commands like this and use the shell again

echo "My current directory is: $(pwd)"
My current directory is: /home/baytizzel/Documents

if you've ever done bash scripting this seems straightforward

Redirection > ​

allows you to write stdout to a file

  • note, will overwrite existing files as well

e.g.

ls --help > ls-help.txt

with two >> you will append the file, if it exists, if not it creates it

echo 'hello' >> hello.txt

Redirection < ​

Pass file contents into stdin

tr 'a-z' 'A-Z' < template.yaml
- NAME: Baytizzel 
  EMAIL: [email protected]
  URL: http://unsecure.com

fzf ​

fuzzy finder, allows you to search for files

compgen ​

command to find more commands

compgen -c 

or

compgen -c | less

Cool combinations ​

Fuzzy Find any command within your system and pull up its manual ###Fman

compgen -c | fzf | xargs man

compgen -c | fzf | xargs tldr

Alias ​

Essentially a way to save cool commands

  • Anytime i want to do this, I go to my .bashrc or .zrshc file and add it there

FindBigFiles ​

Find biggest file and directorys in that path (to clean up)

du -ah . | sort -hr | head -n 10

deleteNodeProj ​

find and delete Big files due to node projects

find . -name 'node_modules' -type d |
	xargs du -sh |
	sort -hr |
	fzf -m --header "Select whcih ones to delete" --preview 'cat $(dirname {})/package.json' |
	awk '{print $2}' |
	xargs -r rm -rf

history ​

previous command runs

Jobs and running command ​

Useful shell hotkeys ​

ctrl+C -> kills active process
ctrl+d -> quit shell
ctrl+l -> clear screen
ctrl+z -> put process in bg (use fg to bring to foreground)
ctrl+a -> go to front of line
ctrl+e -> go to end of line
ctrl+f -> go forward one char
ctrl+b -> go backward one char
alt+f  -> go forward one word
alt+b  -> go backward one word
ctrl+u -> delete everything before cursor
ctrl+k -> delete everything after cursor
!!     -> run previous command
!      -> used w/ command to get most recent command !<command> 
ctrl+x -> open line in $EDITOR
ctrl+e \/

tips to remember ​

  1. Use the man pages (or tldr) for commands
  2. Use pipelines and subshells to make life easier
  3. Use aliases and scripts to save your work
  4. Use fzf