# Page

## Using Bash Parameter Expansion

### **Lowercase Conversion**

To convert a string to lowercase, use the **{variable,,}** syntax:

```bash
string="Hello, World!"
lowercase_string="${string,,}"
echo "$lowercase_string"
```

Output:

```
Output:
hello, world!
```

### **Uppercase Conversion**

To convert a string to uppercase, use the **{variable^^}** syntax:

```bash
string="Hello, World!"
uppercase_string="${string^^}"
echo "$uppercase_string"
```

Output:

```
HELLO, WORLD!
```

## Using the \`tr\` Command

The **tr (translate)** command is a versatile tool for transforming text. It can be used for case conversion by specifying the input and output character sets:

### **Lowercase Conversion**

```bash
string="Hello, World!"
lowercase_string=$(echo "$string" | tr '[:upper:]' '[:lower:]')
echo "$lowercase_string"
```

Output:

```
hello, world!
```

### **Uppercase Conversion**

```
string="Hello, World!"
uppercase_string=$(echo "$string" | tr '[:lower:]' '[:upper:]')
echo "$uppercase_string"


Output:

HELLO, WORLD!
```

Output:

```
HELLO, WORLD!
```

<https://tecadmin.net/string-case-conversion-in-bash/>