shell-snippets

Shell Snippets

Source

https://youtu.be/Z56Jmr9Z34Q

https://youtu.be/kgII-YWo3Zw

https://youtu.be/a6Q8Na575qc

https://youtu.be/sz_dsktIjt4

Example

Standard

• date
• echo 'Hello World
• echo $PATH
• which echo
• --help
• sudo
• convert image.png image.jpg
• man mv (Show manuel for the move command, close with cmd -q)

Navigation

• pwd (print working directory)
• cd (change directory)
• cd .. (one directory back)
• cd ./home (change directory in the current directory
• ls (Lists files in the directory)
• ls -l (List files with extra information)
• ls -R (List only the directories with paths)
• ls *.sh (Only files with .sh extension)
• cd ~ (Goes to home directory)
• cd - (Goes to the previous directory)
• mv current-name-folder new-name-folder (Change name or file of folder)
• cp (copy)
• rm (remove)
• clear (control l - also works)
• find . -name test-folder -type d (find in current directory with name 'test-folder' and type 'directory')
• find . -name "*.txt" (find all files with the .txt extension)
• find . -name "*.txt -exec rm {} ; (remove those files)
• grep again hello.txt (Check the string in the file of hello.txt)
• history (prints out all the executed commands)
• history 1 | grep mkdir (print out all the executed commands of 'mkdir')
• tree (show tree of the current directory)

Creation

• echo "Hello" > hello.txt (creates file with hello) in current directory
• echo "Hello Again." > hello.txt (appents the file with new content)
• cat hello.txt (prints content of a file)
• ls | >> hello.txt (pipe)
• open hello.txt (open a file)
• open ./ (open current folder)
• source mcd.sh (load a script into your shell
• touch exmaple
• touch example-1 example-2
• touch example-{3,4,5}

Scripting in Bash

Working with values

foo=bar
echo $foo
# Prints out: 'Bar'

echo "Value is $foo"
# Print out: "Value is bar"

echo 'Value is $foo'
# Print out: "Value is $foo"

---

Creating a shell script

mcd () {
    mkdir -p "$1"
    cd "$1"
}

$1 is the first variable of a shell script.

$0 is the name of the file script itself.

---

Example.sh script that check files for foobar

#/bin/bash

echo "Starting program at $(date)"

echo "Running program $0 with $# arguments with pid $$"

for file in "$@"; do
    grep foobar "$file" > /dev/null 2> /dev/null
    if [[ "$?" -ne 0]]; then
        echo "File $file does not have foobar, adding one"
        echo "# foobar" >> "$file"
    fi
done

Extra Information

Absolute Paths vs Relative Paths

Spaces are reserved with Scripting is Bash

Single space don't take in account variables

PID means process id $$

Data Wrangling, formatting data