Bash

Automation Scripts

In ML_Tools, see: Bash_folder

Basic Commands

Show Current Directory:
```
pwd
```
Display Contents of a Text File:
```
cat filename.txt
```
Search for a Word in a File:
```
[[grep]] "word" filename.txt
```
Replace Text in a File (Output Only):
```
sed 's/old/new/g' filename.txt
```

Writing and Running a Bash Script

Create a Script:

nano hello.sh

Add:

#!/bin/bash
echo "Hello, $(whoami)! Welcome to Bash scripting!"

Save and exit: Ctrl + O, Enter, Ctrl + X.

Make the Script Executable:
```
chmod +x hello.sh
```
Run the Script:
```
./hello.sh
```

Useful Bash Automation Tips

Clear Screen:
```
clear
```
Keyboard Shortcut: Ctrl + L.
Clear Screen and Command History:
```
clear && history -c
```
Reset Terminal:
```
reset
```

Managing Command History

Clear Current Session’s History:
```
history -c
```
Save History to a Custom File:
```
history > my_session_history.txt
```
Clear and Remove Saved History:
```
history -c
> ~/.bash_history
```
Start a Fresh Bash Session:
```
exec bash
```

Example: Conditional Execution

if [ -f filename.txt ]; then
  echo "File exists."
else
  echo "File does not exist."
fi

If you want to learn more bash, explore:

See these concepts:

Shebang: #!/bin/bash
Variables: $PI_IP, ${variable}
Conditionals: if [ condition ]; then
Loops: for, while
Functions: function_name() {}
Command substitution: $(command)
Redirects: >, >>, 2>&1

See these concepts:

Function definitions and exports
Color codes (ANSI escape sequences)
Command piping: |
SSH with command execution
Error checking: $?
Configuration files
Heredocs: << 'EOF'