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bash | string | uppercase | lowercase

Using Bash Parameter Expansion

Lowercase Conversion

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

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:

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

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/