Linux/BASH

Shebang

```
#!/bin/bash
```

Output & Piping

output to file

command > file.txt             # redirect output
command >> file.txt            # append to file

command &> file.txt            # stdout and stderr to file
command &>> file.txt           # stdout and stderr append to file

command 2> file.txt            # stderr to file
command 2>> file.txt           # stderr append to file

command | tee -a file.txt      # stdout to terminal and file (append)
command |& tee -a file.txt     # stdout+stderr to terminal and file (append)

redirecting output

command 2>&1 >/dev/null        # stderr to stdout and stdout to null

If

if [ condition ]
  then command1
  else command2
fi